Systems and methods for controlling an engine start in a hybrid vehicle

ABSTRACT

Methods and systems are provided for operating a driveline of a hybrid vehicle that includes an internal combustion engine, an electric machine, and a transmission, where the transmission is downstream of the engine, and where the electric machine is downstream of the transmission. In one example, while the vehicle is being propelled solely via the electric machine, one or more gears of the transmission may be pre-engaged or selected, to prepare the driveline for an engine start event. In this way, driveline torque disturbance and delays in torque requests may be reduced or avoided upon a request for an engine start event.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional PatentApplication No. 62/463,472, filed Feb. 24, 2017. The entire contents ofthe above-referenced application are hereby incorporated by reference inits entirety for all purposes.

FIELD

The present description relates generally to methods and systems forcontrolling a transmission during a rolling hybrid engine start event.

BACKGROUND/SUMMARY

For a hybrid vehicle utilizing an internal combustion engine coupled toa step ratio transmission (e.g. conventional planetary automatictransmission, automated single clutch manual, dual clutch transmission,etc.), with at least one electric machine delivering torque to drivenwheels after the transmission, there can be powertrain modes that propelthe vehicle using only the electric machine with the transmission inputcoupling open, allowing the engine to be stationary and off. If thevehicle is being driven in such a mode at non-zero speeds, and a totalpowertrain output torque request exceeds the propulsion capability ofthe electric motor(s), the engine may need to be started and connectedto the driveline to deliver additional torque. The inventors have hereinrecognized that adding engine torque to driven wheels should be donesmoothly and as quickly as possible to reduce delays between a vehicleoperator's input and/or expectations, and the actual vehicleacceleration response. In some cases, the engine may need to beconnected to driven wheels through a higher transmission gear ratio toachieve higher torque multiplication, to meet high total powertrainoutput torque requests. At lower powertrain output torque request, theengine may be connected at a lower transmission gear ratio to reduceengine seed, sound volume, and potential driveline disturbance atconnection. At higher vehicle speeds, a higher gear ratio may result ina higher input shaft rotational speed that the engine may need to matchto lock the input clutch and transmit the requested torque to drivenwheels. Since the engine is starting from zero speed, it may take sometime to start combustion and accelerate its inertia up to a desiredspeed to connect the engine to the transmission input. While the engineis accelerating up to the target speed, it may not transmit any torqueto the driven wheels, resulting in a delay between a request for enginetorque and the engine transmitting torque to the wheels. If the enginequickly connects to the transmission input, but the transmission is inthe wrong gear, an additional time delay may result for the transmissionto shift to the appropriate gear ratio to meet the required drivetraintorque after the engine connects. If the vehicle is in neutral with nointernal shift elements engaged to connect the transmission input to theoutput, the transmission must first shift into the appropriate gearratio before the engine can be connected. This adds additional delay tothe total driveline torque response, and additional torque must be takenfrom the driveline (electric motor, vehicle inertia, etc.) to acceleratethe rotating inertia of the internal components of the transmission tolock the desired gear before the engine may be connected. The torque forcompleting such a shift may reduce an acceleration capability of thevehicle being propelled by the electric machine before the engine hasbeen connected to the driveline.

An optimal vehicle response may be achieved if the transmission is in anoptimal gear at a time when the engine connects to the driveline. Such aresponse may be further improved if the transmission is in an optimalgear prior to the engine being commanded to start and connect to thedriveline as there may not be any time or energy lost due to shiftingthe transmission into an optimal gear for connection during the enginestarting process. The inventors have thus herein developed systems andmethods to at least partially address the above-mentioned issues. In oneexample a driveline operating method comprises propelling a vehiclesolely via an electric machine while an engine of the vehicle is off andnot connected to a transmission, the electric machine positioned in thedriveline downstream of the transmission, and engaging one or more gearsof the transmission with the engine off, to prepare the driveline for anengine start event to meet a vehicle operator torque request.

In one example of the method, engaging one or more gears furthercomprises engaging one or more gears with a lowest torque multiplicationavailable that allows an input shaft to the transmission to remain abovean engine idle speed while the vehicle is propelled solely via theelectric machine. In such an example, the method may further compriseshifting the one or more gears to another gear to meet the vehicleoperator torque request prior to connecting the engine to thetransmission.

In another example of the method, the method may further comprisepredicting vehicle operating conditions that may result in the enginestart event. In such an example, vehicle operating conditions thatresult in the engine start event may include a minimum accelerator pedalposition and a current vehicle speed. In some examples, engaging the oneor more gears of the transmission may further comprise engaging a targetgear comprising an optimal gear for connecting the engine to thetransmission at the time of the engine start event.

In another example, engaging one or more gears of the transmission mayfurther comprise additionally engaging a non-target gear, where thetransmission comprises a dual clutch transmission. In such an example,the non-target gear may comprise a sequentially lower gear than thetarget gear, provided that the target gear is not the lowest availablegear. In another example the non-target gear may comprise a sequentiallyhigher gear than the target gear, provided that the target gear is notthe highest available gear.

An example, the target gear may comprise an optimal gear for connectingthe engine to the transmission at the time of the engine start event,and where the non-target gear may correspond to an appropriate gearratio for a current accelerator pedal position and vehicle speed.Furthermore, engaging the one or more gears in the above-mentionedexamples may include operating an electric transmission pump to providehydraulic fluid to actuate one or more shift elements of thetransmission. The above advantages and other advantages, and features ofthe present description will be readily apparent from the followingDetailed Description when taken alone or in connection with theaccompanying drawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a hybrid vehicle driveline.

FIG. 1B is a sketch of an engine of the hybrid vehicle driveline.

FIG. 2 is a schematic diagram of the hybrid vehicle driveline includingcontrollers of various driveline components.

FIG. 3 is a schematic diagram of a dual clutch transmission located inthe hybrid vehicle driveline.

FIG. 4 shows an example timeline illustrating a delay between a requestfor engine torque, and the engine transmitting torque to driven wheels.

FIG. 5 shows a high level flowchart for an example method for avoiding adelay between a request for engine torque, and the engine transmittingtorque to driven wheels.

FIG. 6 shows an example timeline illustrating an avoidance of a delaybetween a request for engine torque, and the engine transmitting torqueto driven wheels, according to the method of FIG. 5.

FIG. 7 shows a high level flowchart for an example method for selectinggears while a vehicle is operating in an electric-only mode ofoperation, which may be utilized in conjunction with the method of FIG.5.

FIG. 8 shows a high level flowchart for an example method for predictinga target gear and selecting the target gear while the vehicle isoperating in an electric-only mode of operation, which may be utilizedin conjunction with the method of FIG. 5.

FIG. 9 shows a high level flowchart for an example method for predictinga target gear and selecting both the target gear and a non-target gearwhile the vehicle is operating in an electric-only mode of operation,which may be utilized in conjunction with the method of FIG. 5.

FIGS. 10-11 show block diagrams for controlling clutch capacity andengine speed to avoid a delay between a request for engine torque, andthe engine transmitting torque to driven wheels, which may be utilizedin conjunction with the method of FIG. 5.

FIG. 12 shows a high level flowchart for an example method forpredicting and engaging a target gear, and in some examples, anon-target gear, while a vehicle is operating in an electric mode ofoperation.

FIG. 13 shows another example of a high level flowchart for an examplemethod for conducting an engine start where one or more gears arepreselected prior to the engine start.

FIG. 14 shows an example timeline for conducting an engine start event,according to the method depicted above at FIG. 13.

DETAILED DESCRIPTION

The following description relates to systems and methods for controllinga dual clutch transmission during a rolling hybrid engine start event.FIGS. 1A-3 show an example hybrid vehicle system that includes adriveline with a motor, an integrated starter/generator, a dual clutchtransmission, and an electric machine that is positioned downstream ofthe dual clutch transmission. It may be understood that herein,downstream of the dual clutch transmission is relative to positivetorque flow from the engine to vehicle wheels, for example.

FIGS. 4-6 describe and show ways to reduce a plateau in vehicleacceleration during an engine start event, where the engine start eventis in response to a vehicle operator demanded wheel torque exceeding acapacity of the electric machine. Briefly, a vehicle accelerationplateau may be reduced via transmitting engine torque through thetransmission via a low speed input shaft of the dual clutchtransmission, while at the same instance engine speed is increasing to atarget engine speed. FIGS. 7-9 describe ways of preselecting differentgear ratios of the dual clutch transmission while the vehicle isoperating solely in an electric mode of operation, to prepare for anengine start event. FIGS. 10-11 show and describe ways of controllingclutch capacity of the dual clutch transmission in order to transientlytransmit engine torque through the dual clutch transmission via thesecond input shaft while engine speed is increasing to the target enginespeed. These various ways of preselecting and controlling can be usedtogether in various combinations and/or separately, if desired.

FIG. 12 describes and shows methods for predicting and engaging a targetgear, and in examples where a vehicle transmission comprises a dualclutch transmission, a non-target gear, while the vehicle is beingpropelled solely via electric power, in preparation for an engine startevent. The method of FIG. 12 may be used in conjunction with the methodof FIG. 5, for example. In one example of the method depicted at FIG.12, target and non-target gears may be selected based on an engine startevent where a wheel torque demand comprises a vehicle operator steppingfully into an accelerator pedal. In such an example, the preselectedgears may not be appropriate for an engine start request due to arequest for cabin heating/cooling, battery charging, etc. In such anexample, a gear shift may be conducted in response to such a request,according to the method of FIG. 13. FIG. 14 shows an example timelinefor preselecting gears and shifting to an appropriate gear responsive toan engine start request involving a request for cabin heating/cooling,battery charge maintenance, etc.

FIG. 1A illustrates an example vehicle propulsion system 100 for vehicle121. Vehicle propulsion system 100 includes at least two power sourcesincluding an internal combustion engine 110 and an electric machine 120.Electric machine 120 may be configured to utilize or consume a differentenergy source than engine 110. For example, engine 110 may consumeliquid fuel (e.g. gasoline) to produce an engine output while electricmachine 120 may consume electrical energy to produce an electric machineoutput. As such, a vehicle with propulsion system 100 may be referred toas a hybrid electric vehicle (HEV). Throughout the description of FIG.1A, mechanical connections between various components is illustrated assolid lines, whereas electrical connections between various componentsare illustrated as dashed lines.

Vehicle propulsion system 100 has a front axle (not shown) and a rearaxle 122. In some examples, rear axle may comprise two half shafts, forexample first half shaft 122 a, and second half shaft 122 b. Vehiclepropulsion system 100 further has front wheels 130 and rear wheels 131.The rear axle 122 is coupled to electric machine 120 and transmission125, via which the rear axle 122 may be driven. The rear axle 122 may bedriven either purely electrically and exclusively via electric machine120 (e.g., electric only drive or propulsion mode, engine is notcombusting air and fuel or rotating), in a hybrid fashion via electricmachine 120 and engine 110 (e.g., parallel mode), or exclusively viaengine 110 (e.g., engine only propulsion mode), in a purely combustionengine-operated fashion. Rear drive unit 136 may transfer power fromengine 110 or electric machine 120, to axle 122, resulting in rotationof drive wheels 131. Rear drive unit 136 may include a gear set and oneor more clutches to decouple transmission 125 and electric machine 120from wheels 131.

A transmission 125 is illustrated in FIG. 1A as connected between engine110, and electric machine 120 assigned to rear axle 122. In one example,transmission 125 is a dual clutch transmission (DCT). In an examplewherein transmission 125 is a DCT, DCT may include a first clutch 126, asecond clutch 127, and a gear box 128. DCT 125 outputs torque to driveshaft 129 to supply torque to wheels 131. As will be discussed infurther detail below with regard to FIG. 3, transmission 125 may shiftgears by selectively opening and closing first clutch 126 and secondclutch 127. It may be understood that opening and closing of firstclutch 126 and second clutch 127 may be conducted hydraulically, forexample. In other words, controlling a torque capacity of first clutch,or controlling a torque capacity of second clutch 127 may be conductedby controlling an application pressure of a fluid to first clutch 126and/or second clutch 127.

Electric machine 120 may receive electrical power from onboard energystorage device 132. Furthermore, electric machine 120 may provide agenerator function to convert engine output or the vehicle's kineticenergy into electrical energy, where the electrical energy may be storedat energy storage device 132 for later use by the electric machine 120or integrated starter/generator 142. A first inverter system controller(ISC1) 134 may convert alternating current generated by electric machine120 to direct current for storage at the energy storage device 132 andvice versa.

In some examples, energy storage device 132 may be configured to storeelectrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including cabinheating and air conditioning, engine starting, headlights, cabin audioand video systems, etc. As a non-limiting example, energy storage device132 may include one or more batteries and/or capacitors.

Control system 14 may communicate with one or more of engine 110,electric machine 120, energy storage device 132, integratedstarter/generator 142, transmission 125, etc. Control system 14 mayreceive sensory feedback information from one or more of engine 110,electric machine 120, energy storage device 132, integratedstarter/generator 142, transmission 125, etc. Further, control system 14may send control signals to one or more of engine 110, electric machine120, energy storage device 132, transmission 125, etc., responsive tothis sensory feedback. Control system 14 may receive an indication of anoperator requested output of the vehicle propulsion system from a humanoperator 102, or an autonomous controller. For example, control system14 may receive sensory feedback from pedal position sensor 194 whichcommunicates with pedal 192. Pedal 192 may refer schematically to anaccelerator pedal. Similarly, control system 14 may receive anindication of an operator requested vehicle braking via a human operator102, or an autonomous controller. For example, control system 14 mayreceive sensory feedback from pedal position sensor 157 whichcommunicates with brake pedal 156.

Energy storage device 132 may periodically receive electrical energyfrom a power source 180 (e.g., a stationary power grid) residingexternal to the vehicle (e.g., not part of the vehicle) as indicated byarrow 184. As a non-limiting example, vehicle propulsion system 100 maybe configured as a plug-in hybrid electric vehicle (HEV), wherebyelectrical energy may be supplied to energy storage device 132 frompower source 180 via an electrical energy transmission cable 182. Duringa recharging operation of energy storage device 132 from power source180, electrical transmission cable 182 may electrically couple energystorage device 132 and power source 180. In some examples, power source180 may be connected at inlet port 150. Furthermore, in some examples, acharge status indicator 151 may display a charge status of energystorage device 132.

In some examples, electrical energy from power source 180 may bereceived by charger 152. For example, charger 152 may convertalternating current from power source 180 to direct current (DC), forstorage at energy storage device 132. Furthermore, a DC/DC converter 153may convert a source of direct current from charger 152 from one voltageto another voltage. In other words, DC/DC converter 153 may act as atype of electric power converter.

While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 182 may be disconnected between powersource 180 and energy storage device 132. Control system 14 may identifyand/or control the amount of electrical energy stored at the energystorage device, which may be referred to as the state of charge (SOC).

In other examples, electrical transmission cable 182 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 132 from power source 180. For example, energy storage device 132may receive electrical energy from power source 180 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 132 from a power source that doesnot comprise part of the vehicle. In this way, electric machine 120 maypropel the vehicle by utilizing an energy source other than the fuelutilized by engine 110.

Electric energy storage device 132 includes an electric energy storagedevice controller 139 and a power distribution module 138. Electricenergy storage device controller 139 may provide charge balancingbetween energy storage element (e.g., battery cells) and communicationwith other vehicle controllers (e.g., controller 12). Power distributionmodule 138 controls flow of power into and out of electric energystorage device 132.

Vehicle propulsion system 100 may also include an ambienttemperature/humidity sensor 198, and sensors dedicated to indicating theoccupancy-state of the vehicle, for example onboard cameras 105, seatload cells 107, and door sensing technology 108. Vehicle system 100 mayalso include inertial sensors 199. Inertial sensors 199 may comprise oneor more of the following: longitudinal, latitudinal, vertical, yaw,roll, and pitch sensors (e.g., accelerometers). Axes of yaw, pitch,roll, lateral acceleration, and longitudinal acceleration are asindicated. As one example, inertial sensors 199 may couple to thevehicle's restraint control module (RCM) (not shown), the RCM comprisinga subsystem of control system 14. The control system may adjust engineoutput and/or the wheel brakes to increase vehicle stability in responseto sensor(s) 199. In another example, the control system may adjust anactive suspension system 111 responsive to input from inertial sensors199. Active suspension system 111 may comprise an active suspensionsystem having hydraulic, electrical, and/or mechanical devices, as wellas active suspension systems that control the vehicle height on anindividual corner basis (e.g., four corner independently controlledvehicle heights), on an axle-by-axle basis (e.g., front axle and rearaxle vehicle heights), or a single vehicle height for the entirevehicle. Data from inertial sensor 199 may also be communicated tocontroller 12, or alternatively, sensors 199 may be electrically coupledto controller 12.

One or more tire pressure monitoring sensors (TPMS) may be coupled toone or more tires of wheels in the vehicle. For example, FIG. 1A shows atire pressure sensor 197 coupled to wheel 131 and configured to monitora pressure in a tire of wheel 131. While not explicitly illustrated, itmay be understood that each of the four tires indicated in FIG. 1A mayinclude one or more tire pressure sensor(s) 197. Furthermore, in someexamples, vehicle propulsion system 100 may include a pneumatic controlunit 123. Pneumatic control unit may receive information regarding tirepressure from tire pressure sensor(s) 197, and send said tire pressureinformation to control system 14. Based on said tire pressureinformation, control system 14 may command pneumatic control unit 123 toinflate or deflate tire(s) of the vehicle wheels. While not explicitlyillustrated, it may be understood that pneumatic control unit 123 may beused to inflate or deflate tires associated with any of the four wheelsillustrated in FIG. 1A. For example, responsive to an indication of atire pressure decrease, control system 14 may command pneumatic controlsystem unit 123 to inflate one or more tire(s). Alternatively,responsive to an indication of a tire pressure increase, control system14 may command pneumatic control system unit 123 to deflate tire(s) oneor more tires. In both examples, pneumatic control system unit 123 maybe used to inflate or deflate tires to an optimal tire pressure ratingfor said tires, which may prolong tire life.

One or more wheel speed sensors (WSS) 195 may be coupled to one or morewheels of vehicle propulsion system 100. The wheel speed sensors maydetect rotational speed of each wheel. Such an example of a WSS mayinclude a permanent magnet type of sensor.

Vehicle propulsion system 100 may further include an accelerometer 20.Vehicle propulsion system 100 may further include an inclinometer 21.

Vehicle propulsion system 100 may further include a starter 140. Starter140 may comprise an electric motor, hydraulic motor, etc., and may beused to rotate engine 110 so as to initiate engine 110 operation underits own power.

Vehicle propulsion system 100 may further include a brake system controlmodule (BSCM) 141. In some examples, BSCM 141 may comprise an anti-lockbraking system or anti-skid braking system, such that wheels (e.g. 130,131) may maintain tractive contact with the road surface according todriver inputs while braking, which may thus prevent the wheels fromlocking up, to prevent skidding. In some examples, BSCM may receiveinput from wheel speed sensors 195.

Vehicle propulsion system 100 may further include a belt integratedstarter generator (BISG) 142. BISG may produce electric power when theengine 110 is in operation, where the electrical power produced may beused to supply electric devices and/or to charge the onboard storagedevice 132. As indicated in FIG. 1A, a second inverter system controller(ISC2) 143 may receive alternating current from BISG 142, and mayconvert alternating current generated by BISG 142 to direct current forstorage at energy storage device 132. Integrated starter/generator 142may also provide torque to engine 110 during engine starting or otherconditions to supplement engine torque.

Vehicle propulsion system 100 may further include a power distributionbox (PDB) 144. PDB 144 may be used for routing electrical powerthroughout various circuits and accessories in the vehicle's electricalsystem.

Vehicle propulsion system 100 may further include a high current fusebox (HCFB) 145, and may comprise a variety of fuses (not shown) used toprotect the wiring and electrical components of vehicle propulsionsystem 100.

Vehicle propulsion system 100 may further include a motor electronicscoolant pump (MECP) 146. MECP 146 may be used to circulate coolant todiffuse heat generated by at least electric machine 120 of vehiclepropulsion system 100, and the electronics system. MECP may receiveelectrical power from onboard energy storage device 132, as an example.

Controller 12 may comprise a portion of a control system 14. Controlsystem 14 is shown receiving information from a plurality of sensors 16(various examples of which are described herein) and sending controlsignals to a plurality of actuators 81 (various examples of which aredescribed herein). As one example, sensors 16 may include tire pressuresensor(s) 197, wheel speed sensor(s) 195, ambient temperature/humiditysensor 198, onboard cameras 105, seat load cells 107, door sensingtechnology 108, inertial sensors 199, etc. In some examples, sensorsassociated with engine 110, transmission 125, electric machine 120,etc., may communicate information to controller 12, regarding variousstates of engine, transmission, and motor operation, as will bediscussed in further detail with regard to FIGS. 1B-3.

Vehicle propulsion system 100 may further include a positive temperaturecoefficient (PTC) heater 148. As an example, PTC heater 148 may comprisea ceramic material such that when resistance is low, the ceramicmaterial may accept a large amount of current, which may result in arapid warming of the ceramic element. However, as the element warms andreaches a threshold temperature, the resistance may become very large,and as such, may not continue to produce much heat. As such, PTC heater148 may be self-regulating, and may have a good degree of protectionfrom overheating.

Vehicle propulsion system 100 may further include an air conditioningcompressor module 149, for controlling an electric air conditioningcompressor (not shown).

Vehicle propulsion system 100 may further include a vehicle audiblesounder for pedestrians (VASP) 154. For example, VASP 154 may beconfigured to produce audible sounds via sounders 155. In some examples,audible sounds produced via VASP 154 communicating with sounders 155 maybe activated responsive to a vehicle operator triggering the sound, orautomatically, responsive to engine speed below a threshold or detectionof a pedestrian.

Vehicle propulsion system 100 may also include an on-board navigationsystem 17 (for example, a Global Positioning System) on dashboard 19that an operator of the vehicle may interact with. The navigation system17 may include one or more location sensors for assisting in estimatinga location (e.g., geographical coordinates) of the vehicle. For example,on-board navigation system 17 may receive signals from GPS satellites(not shown), and from the signal identify the geographical location ofthe vehicle. In some examples, the geographical location coordinates maybe communicated to controller 12.

Dashboard 19 may further include a display system 18 configured todisplay information to the vehicle operator. Display system 18 maycomprise, as a non-limiting example, a touchscreen, or human machineinterface (HMI), display which enables the vehicle operator to viewgraphical information as well as input commands. In some examples,display system 18 may be connected wirelessly to the internet (notshown) via controller (e.g. 12). As such, in some examples, the vehicleoperator may communicate via display system 18 with an internet site orsoftware application (app).

Dashboard 19 may further include an operator interface 15 via which thevehicle operator may adjust the operating status of the vehicle.Specifically, the operator interface 15 may be configured to initiateand/or terminate operation of the vehicle driveline (e.g., engine 110,BISG 142, DCT 125, and electric machine 120) based on an operator input.Various examples of the operator ignition interface 15 may includeinterfaces that require a physical apparatus, such as an active key,that may be inserted into the operator ignition interface 15 to startthe engine 110 and turn on the vehicle, or may be removed to shut downthe engine 110 and turn off the vehicle. Other examples may include apassive key that is communicatively coupled to the operator ignitioninterface 15. The passive key may be configured as an electronic key fobor a smart key that does not have to be inserted or removed from theignition interface 15 to operate the vehicle engine 10. Rather, thepassive key may be located inside or proximate to the vehicle (e.g.,within a threshold distance of the vehicle). Still other examples mayadditionally or optionally use a start/stop button that is manuallypressed by the operator to start or shut down the engine 110 and turnthe vehicle on or off. In other examples, a remote engine start may beinitiated remote computing device (not shown), for example a cellulartelephone, or smartphone-based system where a user's cellular telephonesends data to a server and the server communicates with the vehiclecontroller 12 to start the engine.

Referring to FIG. 1B, a detailed view of internal combustion engine 110,comprising a plurality of cylinders, one cylinder of which is shown inFIG. 1B, is shown. Engine 110 is controlled by electronic enginecontroller 111B. Engine 110 includes combustion chamber 30B and cylinderwalls 32B with piston 36B positioned therein and connected to crankshaft40B. Combustion chamber 30B is shown communicating with intake manifold44B and exhaust manifold 48B via respective intake valve 52B and exhaustvalve 54B. Each intake and exhaust valve may be operated by an intakecam 51B and an exhaust cam 53B. The position of intake cam 51B may bedetermined by intake cam sensor 55B. The position of exhaust cam 53B maybe determined by exhaust cam sensor 57B. Intake cam 51B and exhaust cam53B may be moved relative to crankshaft 40B. Intake valves may bedeactivated and held in a closed state via intake valve deactivatingmechanism 59B. Exhaust valves may be deactivated and held in a closedstate via exhaust valve deactivating mechanism 58B.

Fuel injector 66B is shown positioned to inject fuel directly intocylinder 30B, which is known to those skilled in the art as directinjection. Alternatively, fuel may be injected to an intake port, whichis known to those skilled in the art as port injection. Fuel injector66B delivers liquid fuel in proportion to the pulse width of signal fromengine controller 111B. Fuel is delivered to fuel injector 66B by a fuelsystem 175B, which includes a tank and pump. In addition, intakemanifold 44B is shown communicating with optional electronic throttle62B (e.g., a butterfly valve) which adjusts a position of throttle plate64B to control air flow from air filter 43B and air intake 42B to intakemanifold 44B. Throttle 62B regulates air flow from air filter 43B inengine air intake 42B to intake manifold 44B. In some examples, throttle62B and throttle plate 64B may be positioned between intake valve 52Band intake manifold 44B such that throttle 62B is a port throttle.

Distributorless ignition system 88B provides an ignition spark tocombustion chamber 30B via spark plug 92B in response to enginecontroller 111B. Universal Exhaust Gas Oxygen (UEGO) sensor 126B isshown coupled to exhaust manifold 48B upstream of catalytic converter70B in a direction of exhaust flow. Alternatively, a two-state exhaustgas oxygen sensor may be substituted for UEGO sensor 126B.

Converter 70B can include multiple catalyst bricks, in one example. Inanother example, multiple emission control devices, each with multiplebricks, can be used. Converter 70B can be a three-way type catalyst inone example.

Engine controller 111B is shown in FIG. 1B as a conventionalmicrocomputer including: microprocessor unit 102B, input/output ports104B, read-only memory 106B (e.g., non-transitory memory), random accessmemory 108B, keep alive memory 110B, and a conventional data bus. Othercontrollers mentioned herein may have a similar processor and memoryconfiguration. Engine controller 111B is shown receiving various signalsfrom sensors coupled to engine 110, in addition to those signalspreviously discussed, including: engine coolant temperature (ECT) fromtemperature sensor 112B coupled to cooling sleeve 114B; a measurement ofengine manifold pressure (MAP) from pressure sensor 122B coupled tointake manifold 44B; an engine position sensor from a Hall effect sensor118B sensing crankshaft 40B position; a measurement of air mass enteringthe engine from sensor 120B; and a measurement of throttle position fromsensor 58B. Barometric pressure may also be sensed (sensor not shown)for processing by engine controller 111B. In a preferred aspect of thepresent description, engine position sensor 118B produces apredetermined number of equally spaced pulses every revolution of thecrankshaft from which engine speed (RPM) can be determined. Enginecontroller 111B may receive input from human/machine interface 115B(e.g., pushbutton or touch screen display).

During operation, each cylinder within engine 110 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54B closes and intake valve 52B opens. Airis introduced into combustion chamber 30B via intake manifold 44B, andpiston 36B moves to the bottom of the cylinder so as to increase thevolume within combustion chamber 30B. The position at which piston 36Bis near the bottom of the cylinder and at the end of its stroke (e.g.when combustion chamber 30B is at its largest volume) is typicallyreferred to by those of skill in the art as bottom dead center (BDC).During the compression stroke, intake valve 52B and exhaust valve 54Bare closed. Piston 36B moves toward the cylinder head so as to compressthe air within combustion chamber 30B. The point at which piston 36B isat the end of its stroke and closest to the cylinder head (e.g. whencombustion chamber 30B is at its smallest volume) is typically referredto by those of skill in the art as top dead center (TDC). In a processhereinafter referred to as injection, fuel is introduced into thecombustion chamber. In a process hereinafter referred to as ignition,the injected fuel is ignited by known ignition means such as spark plug92B, resulting in combustion. During the expansion stroke, the expandinggases push piston 36B back to BDC. Crankshaft 40B converts pistonmovement into a rotational torque of the rotary shaft. Finally, duringthe exhaust stroke, the exhaust valve 54B opens to release the combustedair-fuel mixture to exhaust manifold 48B and the piston returns to TDC.Note that the above is shown merely as an example, and that intake andexhaust valve opening and/or closing timings may vary, such as toprovide positive or negative valve overlap, late intake valve closing,or various other examples.

FIG. 2 is a block diagram of vehicle 121 including a powertrain ordriveline 200. The powertrain of FIG. 2 includes engine 110 shown inFIGS. 1A-1B. Other components of FIG. 2 that are common with FIG. 1A areindicated by like numerals, and will be discussed in detail below.Powertrain 200 is shown including vehicle system controller 12, enginecontroller 111B, electric machine controller 252, transmissioncontroller 254, energy storage device controller 253, and brakecontroller 141 (also referred to herein as brake system control module).The controllers may communicate over controller area network (CAN) 299.Each of the controllers may provide information to other controllerssuch as torque output limits (e.g. torque output of the device orcomponent being controlled not to be exceeded), toque input limits (e.g.torque input of the device or component being controlled not to beexceeded), torque output of the device being controlled, sensor anactuator data, diagnostic information (e.g. information regarding adegraded transmission, information regarding a degraded engine,information regarding a degraded electric machine, information regardingdegraded brakes). Further, the vehicle system controller 12 may providecommands to engine controller 111B, electric machine controller 252,transmission controller 254, and brake controller 141 to achieve driverinput requests and other requests that are based on vehicle operatingconditions.

For example, in response to a driver releasing an accelerator pedal andvehicle speed decreasing, vehicle system controller 12 may request adesired wheel torque or wheel power level to provide a desired rate ofvehicle deceleration. The desired wheel torque may be provided byvehicle system controller 12 requesting a first braking torque fromelectric machine controller 252 and a second braking torque from brakecontroller 141, the first and second torques providing the desiredbraking torque at vehicle wheels 131.

In other examples, the partitioning of controlling powertrain devicesmay be partitioned differently than is illustrated in FIG. 2. Forexample, a single controller may take the place of vehicle systemcontroller 12, engine controller 111B, electric machine controller 252,transmission controller 254, and brake controller 141. Alternatively,the vehicle system controller 12 and the engine controller 111B may be asingle unit while the electric machine controller 252, the transmissioncontroller 254, and the brake controller 141 may be standalonecontrollers.

In this example, powertrain 200 may be powered by engine 110 andelectric machine 120. In other examples, engine 110 may be omitted.Engine 110 may be started with an engine starter (e.g. 140), via beltintegrated starter/generator (BISG) 142, or via electric machine 120. Insome examples, BISG may be coupled directly to the engine crankshaft ateither end (e.g., front or back) of the crankshaft. Electric machine 120(e.g. high voltage electric machine, operated with greater than 30volts), is also referred to herein as electric machine, motor, and/orgenerator. Further, torque of engine 110 may be adjusted via a torqueactuator 204, such as a fuel injector, throttle, etc.

BISG 142 is mechanically coupled to engine 110 via belt 231. BISG 142may be coupled to a crankshaft 40B or a camshaft (not shown). BISG 142may operate as a motor when supplied with electrical power via electricenergy storage device 132, also referred to herein as onboard energystorage device 132. BISG 142 may additionally operate as a generatorsupplying electrical power to electric energy storage device 132.

Driveline 200 includes engine 110 mechanically coupled to dual clutchtransmission (DCT) 125 via crank shaft 40B. DCT 125 includes a firstclutch 126, a second clutch 127, and a gear box 128. DCT 125 outputstorque to shaft 129, to supply torque to vehicle wheels 131.Transmission controller 254 selectively opens and closes first clutch126 and second clutch 127 to shift DCT 125. In some examples, there areno other driveline clutches or disconnect devices other than those shownin FIG. 2. However, in other examples, additional clutches or disconnectdevices may be added, if desired. As discussed above, selectivelyopening/closing first clutch 126 and/or second clutch 127 may comprisecontrolling an application pressure of a fluid to first clutch 126and/or second clutch 127. In other words, first clutch 126 and secondclutch 127 may be hydraulically actuated. Gear box 128 may include aplurality of gears. One clutch, for example first clutch 126 may controlodd gears 261 (e.g. first, third, fifth, and reverse), while anotherclutch, for example second clutch 127, may control even gears 262 (e.g.second, fourth, and sixth). By utilizing such an arrangement, gears canbe changed without interrupting power flow from the engine 110 to dualclutch transmission 125.

Electric machine 120 may be operated to provide torque to powertrain 200or to convert powertrain torque into electrical energy to be stored inelectrical energy storage device 132 in a regeneration mode.Additionally, electric machine 120 may convert the vehicle's kineticenergy into electrical energy for storage in electric energy storagedevice 132. Electric machine 120 is in electrical communication withenergy storage device 132. Electric machine 120 has a higher outputtorque capacity than starter (e.g. 140) depicted in FIG. 1A, or BISG142. Further, electric machine 120 directly drives powertrain 200, or isdirectly driven by powertrain 200.

Electrical energy storage device 132 (e.g. high voltage battery or powersource) may be a battery, capacitor, or inductor. Electric machine 120is mechanically coupled to wheels 131 and dual clutch transmission via agear set in rear drive unit 136 (shown in FIG. 1A). Electric machine 120may provide a positive torque or a negative torque to powertrain 200 viaoperating as a motor or generator as instructed by electric machinecontroller 252.

Further, a frictional force may be applied to wheels 131 by engagingfriction wheel brakes 218. In one example, friction wheel brakes 218 maybe engaged in response to the driver pressing his foot on a brake pedal(e.g. 192) and/or in response to instructions within brake controller141. Further, brake controller 141 may apply brakes 218 in response toinformation and/or requests made by vehicle system controller 12. In thesame way, a frictional force may be reduced to wheels 131 by disengagingwheel brakes 218 in response to the driver releasing his foot from abrake pedal, brake controller instructions, and/or vehicle systemcontroller instructions and/or information. For example, vehicle brakesmay apply a frictional force to wheels 131 via controller 141 as part ofan automated engine stopping procedure.

Vehicle system controller 12 may also communicate vehicle suspensionsettings to suspension controller 280. The suspension (e.g. 111) ofvehicle 121 may be adjusted to critically damp, over damp, or under dampthe vehicle suspension via variable dampeners 281.

Accordingly, torque control of the various powertrain components may besupervised by vehicle system controller 12 with local torque control forthe engine 110, transmission 125, electric machine 120, and brakes 218provided via engine controller 111B, electric machine controller 252,transmission controller 254, and brake controller 141.

As one example, an engine torque output may be controlled by adjusting acombination of spark timing, fuel pulse width, fuel pulse timing, and/orair charge, by controlling throttle (e.g. 62B) opening and/or valvetiming, valve lift and boost for turbo- or super-charged engines. In thecase of a diesel engine, controller 12 may control the engine torqueoutput by controlling a combination of fuel pulse width, fuel pulsetiming, and air charge. In all cases, engine control may be performed ona cylinder-by-cylinder basis to control the engine torque output.

Electric machine controller 252 may control torque output and electricalenergy production from electric machine 120 by adjusting current flowingto and from field and/or armature windings of electric machine 120 as isknown in the art.

Transmission controller 254 may receive transmission output shaft torquefrom torque sensor 272. Alternatively, sensor 272 may be a positionsensor or torque and position sensors. If sensor 272 is a positionsensor, transmission controller 254 may count shaft position pulses overa predetermined time interval to determine transmission output shaftvelocity. Transmission controller 254 may also differentiatetransmission output shaft velocity to determine transmission outputshaft acceleration. Transmission controller 254, engine controller 111B,and vehicle system controller 12, may also receive additionaltransmission information from sensors 277, which may include but are notlimited to pump output line pressure sensors, transmission hydraulicpressure sensors (e.g., gear clutch fluid pressure sensors), motortemperature sensors, BISG temperatures, shift selector position sensors,synchronizer position sensors, first input shaft speed sensor(s), secondinput shaft speed sensor(s), and ambient temperature sensors.Transmission controller may also receive a requested transmission state(e.g., requested gear or park mode) from shift selector 279, which maybe a lever, switches, or other device.

Brake controller 141 receives wheel speed information via wheel speedsensor 195 and braking requests from vehicle system controller 12. Brakecontroller 141 may also receive brake pedal position information frombrake pedal sensor (e.g. 157) shown in FIG. 1A directly or over CAN 299.Brake controller 141 may provide braking responsive to a wheel torquecommand from vehicle system controller 12. Brake controller 141 may alsoprovide anti-lock and vehicle stability braking to improve vehiclebraking and stability. As such, brake controller 141 may provide a wheeltorque limit (e.g., a threshold negative wheel torque not to beexceeded) to the vehicle system controller 12 so that negative motortorque does not cause the wheel torque limit to be exceeded. Forexample, if controller 12 issues a negative wheel torque limit of 50N-m, motor torque may be adjusted to provide less than 50 N-m (e.g., 49N-m) of negative torque at the wheels, including accounting fortransmission gearing.

Positive torque may be transmitted to vehicle wheels 131 in a directionstarting at engine 110 and ending at wheels 131. Thus, according to thedirection of positive torque flow in driveline 200, engine 110 ispositioned in driveline 200 upstream of transmission 125. Transmission125 is positioned upstream of electric machine 120, and BISG 142 may bepositioned upstream of engine 110, or downstream of engine 110 andupstream of transmission 125.

FIG. 3 shows a detailed illustration of a dual clutch transmission (DCT)125. Engine crankshaft 40B is illustrated as coupling to a clutchhousing 393. Alternatively, a shaft may couple crankshaft 40B to clutchhousing 393. Clutch housing 393 may spin in accordance with rotation ofcrankshaft 40B. Clutch housing 393 may include a first clutch 126 and asecond clutch 127. Furthermore, each of first clutch 126 and secondclutch 127 have an associated first clutch plate 390, and a secondclutch plate 391, respectively. In some examples, the clutches maycomprise wet clutches, bathed in oil (for cooling), or dry plateclutches. Engine torque may be transferred from clutch housing 393 toeither first clutch 126 or second clutch 127. First transmission clutch126 transfers torque between engine 110 (shown in FIG. 1A) and firsttransmission input shaft 302. As such, clutch housing 393 may bereferred to as an input side of first transmission clutch 126 and 126Amay be referred to as an output side of first transmission clutch 126.Second transmission clutch 127 transfers torque between engine 110(shown in FIG. 1A) and second transmission input shaft 304. As such,clutch housing 393 may be referred to as an input side of secondtransmission clutch 127 and 127A may be referred to as an output side ofsecond transmission clutch 127.

A gear box 128 may include a plurality of gears, as discussed above.There are two transmission input shafts, including first transmissioninput shaft 302, and second transmission input shaft 304. Secondtransmission input shaft 304 is hollow, while first transmission inputshaft 302 is solid, and sits coaxially within the second transmissioninput shaft 304. As an example, first transmission input shaft 302 mayhave a plurality of fixed gears. For example, first transmission inputshaft 302 may include first fixed gear 306 for receiving first gear 320,third fixed gear 310 for receiving third gear 324, fifth fixed gear 314for receiving fifth gear 329, and seventh fixed gear 318 for receivingseventh gear 332. In other words, first transmission input shaft 302 maybe selectively coupled to a plurality of odd gears. Second transmissioninput shaft 304 may include second fixed gear 308 for receiving secondgear 322, or a reverse gear 328, and may further include fourth fixedgear 316, for receiving either fourth gear 326 or sixth gear 330. It maybe understood that both first transmission input shaft 302 and secondtransmission input shaft 304 may be connected to each of first clutch126 and second clutch 127 via spines (not shown) on the outside of eachshaft, respectively. In a normal resting state, each of first clutch 302and second clutch 304 are held open, for example via springs (notshown), etc., such that no torque from engine (e.g. 110) may betransmitted to first transmission input shaft 302 or second transmissioninput shaft 304 when each of the respective clutches are in an openstate. Responsive to closing first clutch 126, engine torque may betransmitted to first transmission input shaft 302, and responsive toclosing second clutch 127, engine torque may be transmitted to secondtransmission input shaft 304. During normal operation, transmissionelectronics may ensure that only one clutch is closed at any given time.

Gear box 128 may further include a first layshaft shaft 340, and secondlayshaft shaft 342. Gears on first layshaft shaft 340 and secondlayshaft shaft 342 are not fixed, but may freely rotate. In example DCT125, first layshaft shaft 340 includes first gear 320, second gear 322,sixth gear 330, and seventh gear 332. Second layshaft shaft 342 includesthird gear 324, fourth gear 326, fifth gear 329, and reverse gear 328.Both first layshaft shaft 340 and second layshaft shaft 342 may transfertorque via a first output pinion 350, and a second output pinion 352,respectively, to gear 353. In this way, both layshafts may transfertorque via each of first output pinion 350 and second output pinion 352,to output shaft 362, where output shaft may transfer torque to a reardrive unit 136 (shown in FIG. 1A) which may enable each of the drivenwheels (e.g. 131 of FIG. 1A) to rotate at different speeds, for examplewhen performing turning maneuvers.

As discussed above, each of first gear 320, second gear 322, third gear324, fourth gear 326, fifth gear 329, sixth gear 330, seventh gear 332,and reverse gear 328 are not fixed to layshafts (e.g. 340 and 342), butinstead may freely rotate. As such, synchronizers may be utilized toenable each of the gears to match the speed of the layshafts, and mayfurther be utilized to lock the gears. In example DCT 125, foursynchronizers are illustrated, for example, first synchronizer 370,second synchronizer 374, third synchronizer 380, and fourth synchronizer382. First synchronizer 370 includes corresponding first selector fork372, second synchronizer 374 includes corresponding selector fork 376,third synchronizer 380 includes corresponding third selector fork 378,and fourth synchronizer 384 includes corresponding fourth selector fork382. Each of the selector forks may enable movement of eachcorresponding synchronizer to lock one or more gears, or to unlock oneor more gears. For example, first synchronizer 370 may be utilized tolock either first gear 320 or seventh gear 332. Second synchronizer 374may be utilized to lock either second gear 322 or sixth gear 330. Thirdsynchronizer 380 may be utilized to lock either third gear 324 or fifthgear 329. Fourth synchronizer 384 may be utilized to lock either fifthgear 326, or reverse gear 328. In each case, movement of thesynchronizers may be accomplished via the selector forks (e.g. 372, 376,378, and 382) moving each of the respective synchronizers to the desiredposition.

Movement of synchronizers via selector forks may be carried out viatransmission control module (TCM) 254 and shift fork actuators 388,where TCM 254 may comprise TCM 254 discussed above with regard to FIG.2. Shift (selector) fork actuators may be operated electrically,hydraulically, or a combination of electric and hydraulic. Hydraulicpower may be provided via pump 312 and/or pump 367. In other words,hydraulic power may be provided to control one or more shifting elementsof the transmission, where the one or more shifting elements includesone or more selector fork actuators, and in some examples, one or moresynchronizers. TCM 254 may collect input signals from various sensors,assess the input, and control various actuators accordingly. Inputsutilized by TCM 254 may include but are not limited to transmissionrange (P/R/N/D/S/L, etc.), vehicle speed, engine speed and torque,throttle position, engine temperature, ambient temperature, steeringangle, brake inputs, gear box input shaft speed (for both firsttransmission input shaft 302 and second transmission input shaft 304),vehicle attitude (tilt). The TCM may control actuators via an open-loopcontrol, to allow for adaptive control. For example, adaptive controlmay enable TCM 254 to identify and adapt to clutch engagement points,clutch friction coefficients, and position of synchronizer assemblies.TCM 254 may also adjust first clutch actuator 389 and second clutchactuator 387 to open and close first clutch 126 and second clutch 127.First clutch actuator 389 and second clutch actuator 387 may be operatedelectrically, hydraulically, or a combination of electric and hydraulic.Hydraulic power may be provided via pump 312 and/or pump 367.

First clutch 126 may be cooled via fluid supplied via pump 312 and/orpump 367. Valve 397 may be opened to cool first clutch 126. First clutch126 may be cooled at a rate that is significantly greater when firstclutch is open and valve 397 is open since flow of fluid to first clutch126 may be ten times greater than flow of fluid to first clutch 126 whenfirst clutch 126 is closed. In this example, fluid flow to first clutch126 is via conduit 333, which services valve 398 and other devices.However, in other examples, conduit 333 may be directly coupled to valve397 to provide more precise fluid flow control. Similarly, second clutch127 may be cooled via fluid supplied via pump 312 and/or pump 367. Valve398 may be opened to cool second clutch 127. Second clutch 127 may becooled at a rate that is significantly greater when second clutch isopen and valve 398 is open since flow of fluid to second clutch 127 maybe ten times greater than flow of fluid to second clutch 127 when secondclutch 127 is closed. In this example, fluid flow to second clutch 127is via conduit 333, which services valve 398 and other devices. However,in other examples, conduit 333 may be directly coupled to valve 398 toprovide more precise fluid flow control.

TCM 254 is illustrated as receiving input from various sensors 277. Asdiscussed above with regard to FIG. 2, the various sensors may includepump output line pressure sensors, transmission hydraulic pressuresensors (e.g. gear clutch fluid pressure sensors), motor temperaturesensors, shifter position sensors, synchronizer position sensors, andambient temperature sensors. The various sensors 277 may further includewheel speed sensors (e.g. 195), engine speed sensors, engine torquesensors, throttle position sensors, engine temperature sensors, steeringangle sensors, transmission fork position sensors for detectingpositions of selector forks (e.g. 372, 376, 378, 382), and inertialsensors (e.g. 199). Inertial sensors may comprise one or more of thefollowing: longitudinal, latitudinal, vertical, yaw, roll, and pitchsensors, as discussed above with regard to FIG. 1A.

Sensors 277 may further include an input shaft speed (ISS) sensor, whichmay include a magneto-resistive sensor, and where one ISS sensor may beincluded for each gear box input shaft (e.g. one for first transmissioninput shaft 302 and one for second transmission input shaft 304).Sensors 277 may further include an output shaft speed sensor (OSS),which may include a magneto-resistive sensor, and may be attached tooutput shaft 362. Sensors 277 may further include a transmission range(TR) sensor.

DCT 125 may be understood to function as described herein. For example,when first clutch 126 is actuated closed, engine torque may be suppliedto first transmission input shaft 302. When first clutch 126 is closed,it may be understood that second clutch 127 is open, and vice versa.Depending on which gear is locked when first clutch 126 is closed, powermay be transmitted via the first transmission input shaft 302 to eitherfirst layshaft 340 or second layshaft 342, and may be furthertransmitted to output shaft 362 via either first pinion gear 350 orsecond pinion gear 352. Alternatively, when second clutch 127 is closed,power may be transmitted via the second transmission input shaft 304 toeither first layshaft 340 or second layshaft 342, depending on whichgear is locked, and may be further transmitted to output shaft 362 viaeither first pinion gear 350 or second pinion gear 352. It may beunderstood that when torque is being transferred to one layshaft (e.g.first output shaft 340), the other layshaft (e.g. second output shaft342) may continue to rotate even though only the one shaft is drivendirectly by the input. More specifically, the non-engaged shaft (e.g.second layshaft 342) may continue to rotate as it is driven indirectlyby the output shaft 362 and respective pinion gear (e.g. 352).

DCT 125 may enable preselection of gears, which may thus enable rapidswitching between gears with minimal loss of torque during shifting. Asan example, when first gear 320 is locked via first synchronizer 340,and wherein first clutch 126 is closed (and second clutch 127 is open),power may be transmitted from the engine to first input shaft 302, andto first layshaft 340. While first gear 320 is engaged, second gear 322may simultaneously be locked via second synchronizer 374. Because secondgear 322 is locked, this may rotate second input shaft 304, where thesecond input shaft 304 is speed matched to the vehicle speed in secondgear. In an alternative case where a gear is pre-selected on the otherlayshaft (e.g. second layshaft 342), that layshaft will also rotate asit is driven by output shaft 362 and pinion 352.

When a gear shift is initiated by TCM 254, only the clutches need to beactuated to open first clutch 126 and close second clutch 127.Furthermore, outside the TCM, engine speed may be lowered to match theupshift. With the second clutch 127 closed, power may be transmittedfrom the engine, to second input shaft 304, and to first layshaft 340,and may be further transmitted to output shaft 362 via pinion 350.Subsequent to the shifting of gears being completed, TCM 254 maypre-select the next gear appropriately. For example, TCM 254 maypre-select either a higher or a lower gear, based on input it receivesfrom various sensors 277. In this way, gear changes may be achievedrapidly with minimal loss of engine torque provided to the output shaft362.

Dual clutch transmission 300 may in some examples include a parking gear360. A parking pawl 363 may face parking gear 360. When a shift lever isset to park, park pawl 363 may engage parking gear 360. Engagement ofparking pawl 363 with parking gear 360 may be accomplished via a parkingpawl spring 364, or may be achieved via a cable (not shown), a hydraulicpiston (not shown) or a motor (not shown), for example. When parkingpawl 363 is engaged with parking gear 360, driving wheels (e.g. 130,131) of a vehicle may be locked. On the other hand, responsive to theshift lever being moved from park, to another selection (e.g. drive),parking pawl 363 may move such that parking pawl 363 may be disengagedfrom parking gear 360.

In some examples, an electrically driven transmission pump 312 maysupply hydraulic fluid from transmission sump 311 to compress spring364, in order to release parking pawl 363 from parking gear 360.Electric transmission pump 312 may be powered by an onboard energystorage device (e.g. 132), for example. In some examples, a mechanicallydriven pump 367 may additionally or alternatively supply hydraulic fluidfrom transmission sump 311 to compress spring 364 to release parkingpawl 363 from parking gear 360. While not explicitly illustrated,mechanical pump may be driven by the engine (e.g. 110), and may bemechanically coupled to clutch housing 393. A park pawl valve 361 mayregulate the flow of hydraulic fluid to spring 364, in some examples.

Thus, discussed herein, a dual clutch transmission (DCT) may comprise atransmission that uses two separate clutches for odd and even gear sets.One clutch (e.g. 126) is utilized to transfer engine torque to one inputshaft (e.g. 302), while a separate clutch (e.g. 127) is utilized totransfer engine torque to a separate input shaft (e.g. 304). The dualclutch transmission receives engine torque via an engine crankshaft(e.g. 40B), and outputs torque via an output shaft (e.g. 362).

As discussed above, in certain circumstances there can be powertrainmodes that may propel the vehicle, such as vehicle 121, using only theelectric machine with the transmission input clutches (e.g. 126, 127)open, and where the engine is off. If, while the vehicle is beingpropelled via the electric machine and driver demand exceeds thepropulsion capability of the electric machine, the engine may be startedto deliver additional torque to the driveline. However, as the engine isstarting from zero speed, it may take some time to start combustion andaccelerate its inertia up to a particular speed to lock the appropriateinput clutch. While the engine is accelerating up to the target speed,torque may not be transmitted to the driven wheels, which may result ina delay between the request for engine torque, and the enginetransmitting torque to the wheels.

Accordingly, a system may comprise an engine including a crankshaft, anintegrated starter/generator coupled to the engine, a dual clutchtransmission coupled to the engine including a first target clutch, asecond non-target clutch, a first target input shaft, and a secondnon-target input shaft, and an electric machine coupled to the dualclutch transmission downstream of the dual clutch transmission. Thesystem may include a controller storing executable instructions innon-transitory memory that, when executed, cause the controller to startthe engine via the integrated starter/generator responsive to adriveline torque request exceeding a capability of the electric machine,command the electric machine to an electric machine maximumlimit/threshold, control the first target input shaft to a first targetspeed and control the second non-target input shaft to a secondnon-target speed (the first speed higher than the second speed, andtransmit torque from the engine through the transmission via the secondnon-target input shaft by controlling the second non-target clutch whilean engine speed is increasing to the first target speed.

The system may further comprise additional instructions to stoptransmitting torque from the engine via the second non-target inputshaft by commanding open the second non-target clutch, and commencetransmitting torque from the engine through the transmission via thefirst target input shaft by controlling the first target clutchresponsive to an indication that the engine speed is synchronized withthe first target speed.

The system may further comprise additional instructions to preselect aspeed of either or both of the first target input shaft and the secondnon-target input shaft while the vehicle is being propelled solely viathe electric machine.

The system may further comprise additional instructions to control acapacity of the second non-target clutch while the engine speed isincreasing to the first target speed to enable the engine to increase tothe first target speed in a predetermined amount of time.

The system may further comprise additional instructions to control theengine in a speed mode of operation to increase engine speed to thefirst target speed.

Turning to FIG. 4, an example timeline 400 is shown, illustrating adelay between a request for engine torque, and the engine transmittingtorque to the wheels. Timeline 400 includes plot 405 indicating RPM of avehicle engine (e.g. 110), plot 410, indicating RPM of a dual clutchtransmission odd gear input shaft (e.g. 302), and plot 415, indicatingRPM of a dual clutch transmission even gear input shaft (e.g. 304), overtime. Timeline 400 further includes plot 420, indicating an engine (e.g.110) torque, plot 425, indicating ISG (e.g. 142) torque, plot 430,indicating a dual clutch transmission odd gear clutch torque, plot 435,indicating a dual clutch transmission even gear clutch torque, and plot440, indicating electric machine (e.g. 120) torque, over time. Timeline400 further includes plot 445, indicating vehicle acceleration (m/s/s),over time.

At time t0, the vehicle is traveling via torque from the electricmachine only, illustrated by plot 440. The engine is off, illustrated byplots 405 and 420. The transmission input clutches (e.g. 126, 127) areopen, however the transmission has preselected a first gear (e.g. 320)on the odd shaft (e.g. 302), and a sixth gear (e.g. 330), on the evenshaft (e.g. 304). Thus, RPM of the odd shaft is greater than the RPM ofthe even shaft.

At time t1, the vehicle operator tips-in to a maximum accelerator pedal(e.g. 192) position, thus requesting maximum vehicle performance.Accordingly, between time t1 and t2, the engine is started using theISG, indicated by plot 425, and engine RPM increases, illustrated byplot 405. Furthermore, electric machine (e.g. 120) torque is increasedto a maximum limit (e.g. limit not to be exceeded) to provide maximumelectric performance, illustrated by plot 440. Accordingly, the vehicleaccelerates between time t1 and t2, indicated by plot 445.

Between time t2 and t3, engine torque, illustrated by plot 420, isutilized to match engine speed, illustrated by plot 405, with the firstgear odd input shaft speed, illustrated by plot 410. Furthermore,between time t2 and t3, there is a plateau in vehicle acceleration,illustrated by plot 445. The plateau may be due to the electric machinetorque being saturated at its upper limit/threshold, and where theengine speed is not high enough to connect to the transmission, forexample via odd input shaft clutch (e.g. 126). The plateau may includethe parameter (acceleration in this example) being maintained and/or notvarying by more than 5% over a selected duration.

At time t3, engine speed, illustrated by plot 405 is indicated to matchthe speed of the dual clutch transmission odd gear input shaft (e.g.302), illustrated by plot 410. Accordingly, the first gear input clutchmay be commanded to lock (e.g. close) responsive to the speeds beingsynchronized. More specifically, engine speed being synchronized withthe speed of the dual clutch transmission odd gear input shaft maycomprise speeds within 5% of each other or less. With the first gearinput clutch locked, or commanded closed, engine torque may betransmitted to the driveline through the dual clutch transmission (e.g.125). Thus, between time t3 and t4, odd gear clutch torque is indicatedto increase, indicated by plot 430. More specifically, by closing theodd gear clutch, engine torque may be transmitted to the driven wheelsvia the odd input shaft, resulting in vehicle acceleration, illustratedby plot 445.

As discussed, such a process may result in a significant plateau invehicle acceleration while the electric machine is saturated at itsmaximum torque limit/threshold, and while the engine is not at a highenough speed to connect to the transmission input shaft at the targetgear. Engaging the target gear's input clutch earlier may result in areduction in vehicle acceleration, as driveline torque would be used toaccelerate the engine inertia. In some examples, the plateau may bereduced or eliminated via slowing down the application rate of theelectric machine (e.g. 120) motor torque such that it does not reach itsmaximum torque until the engine is connected. However, while such anaction may reduce or eliminate the vehicle acceleration plateau, theplateau would be reduced or eliminated at the expense of lowering theaverage acceleration across the engine start event, thus reducingoverall performance. Thus, a method for reducing or eliminating theacceleration plateau is desired.

Turning now to FIG. 5, a high-level example method 500 for reducing thedelay, or acceleration plateau, between a request for engine torque, andthe engine transmitting torque to the driven wheels, is shown. Morespecifically, the method may include propelling a vehicle solely via anelectric machine while an engine of the vehicle is not connected to adual clutch transmission, the electric machine positioned in thedriveline downstream of a dual clutch transmission. Discussed herein,propelling the vehicle solely via the electric machine may compriseconditions where the electric machine has torque capacity to meet awheel torque demand, for example.

Responsive to a driveline torque request exceeding a capability of theelectric machine, the engine may be started from rest, to deliveradditional torque to the driveline. In such an example, the method mayinclude controlling a first input shaft of the dual clutch transmissionto a first speed (e.g. target speed) via selecting a first gear,controlling a second input shaft of the dual clutch transmission to asecond speed (e.g. non-target speed) via selecting a second gear, wherethe first speed is higher than the second speed, and transmitting torqueto one or more driven wheels of a vehicle via the engine by connectingan engine crankshaft to the second input shaft via a second clutch whilethe engine is increasing speed to the first speed. Thus, theacceleration plateau may be reduced or eliminated by transmittingpositive torque through the transmission to the driveline via a lowergear ratio input shaft (e.g. second input shaft), while the engine speedis running up to the target (e.g. first input shaft) speed.

Discussed herein, it may be understood that “connecting” an enginecrankshaft to either the first input shaft or the second input shaft maycomprise commanding a capacity of either the first clutch or the secondclutch, respectively, such that engine torque is transferred to thetransmission. In other words, “connecting” an engine crankshaft toeither the first input shaft or the second input shaft may compriseclosing either the first clutch or the second clutch, such that enginetorque is transferred to the transmission. In some examples,“connecting” may comprise a slipping clutch, whereas in other examples,connecting may comprise a clutch that is not slipping. Discussed herein,a slipping clutch may also be referred to as “partially connecting” theengine crankshaft to either the first input shaft or the second inputshaft. Furthermore, it may be understood that “fully disconnecting” anengine crankshaft from either the first input shaft or the second inputshaft may comprise commanding open either the first input clutch or thesecond input clutch, such that no engine torque is transferred to thefirst input shaft, or the second input shaft, respectively. Furthermore,discussed herein, “not connected” when utilized as above in terms of“while an engine of the vehicle is not connected to a dual clutchtransmission” may comprise a situation where both the first input clutchand the second input clutch are open, such that no engine torque may betransferred to either the first input shaft or the second input shaft.For example, method 500 may comprise fully disconnecting the enginecrankshaft from the second input shaft and connecting the enginecrankshaft to the first input shaft responsive to engine speed beingsynchronized with the first, or target, speed.

In one example, method 500 may comprise pre-selecting the first gear andthe second gear while the vehicle is being propelled solely via theelectric machine. In another example, method 500 may comprise shiftingone or more gears of the dual clutch transmission to select the firstgear and the second gear responsive to the driveline torque requestexceeding the capability of the electric machine, discussed in greaterdetail below.

Method 500 will be described with reference to the systems describedherein and shown in FIGS. 1A-3, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 500 may be carried out by acontroller, such as controller 12 in FIG. 1A, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 500 and the rest of the methodsincluded herein may be executed by the controller based on instructionstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1A-3. The controller may employengine system actuators such as ISG (e.g. 142), electric machine (e.g.120), selector forks (e.g. 372, 376, 378, 382), first clutch (e.g. 126),second clutch (e.g. 127), etc., according to the method depicted below.

Method 500 begins at 505 and includes indicating whether a drivetraintorque request exceeds electric machine (e.g. 120) capability while thevehicle is traveling in an electric-only mode of vehicle propulsion.More specifically, exceeding electric machine capability may refer toexceeding a torque capability of the electric machine, for example. Suchan indication may include an accelerator pedal position greater than athreshold, for example. Such an indication may in some examples befurther based on limits of the onboard energy storage device (e.g. 132).If, at 505, drivetrain torque request is not indicated to exceed thecapability of the electric machine, method 500 may proceed to 510. At510, method 500 may include maintaining current vehicle operatingconditions. For example, maintaining current vehicle operatingconditions at 510 may include maintaining the engine off, and mayfurther include maintaining propelling the vehicle solely via theelectric machine.

Returning to 505, responsive to an indication that drivetrain torquerequest exceeds the capability of the electric machine (e.g. 120),method 500 may proceed to 515. At 515, method 500 may include commandingan engine start, and may further include commanding a gear shift on anappropriate input shaft to a target gear (e.g. appropriate target gearratio). More specifically, the engine start may be initiated via the ISG(e.g. 142), and the target gear may be selected by the controllercommanding an appropriate selector fork to lock the target gear. Thetarget gear may be determined as a function of an amount by whichdriveline torque requested exceeds the capability of the electricmachine. Furthermore, while not explicitly illustrated, in some examplesmethod 500 may include additionally selecting a non-target gear, with aresultant lower input shaft speed than that of the target gear inputshaft speed. As an example, the target gear may comprise a first gear(e.g. 320), while the non-target gear may comprise a sixth gear (e.g.330). Importantly, it may be understood that the target gear maycomprise a gear corresponding to one input shaft (e.g. first inputshaft), and the non-target gear may comprise a gear corresponding to theother input shaft (e.g. second input shaft). Furthermore, it may beunderstood that the target gear may correspond to an input shaft speedgreater than the speed of the input shaft corresponding to thenon-target gear.

Step 515 is illustrated as a dashed box, because in some examples, noshifting of gears may be conducted at step 515. For example, the targetgear may already be pre-selected, and in some examples the non-targetgear may additionally already be pre-selected. Strategies forpreselecting one or both of the target gear and non-target gear whilethe vehicle is operating in an electric-only mode, will be described indetail below with regard to the methods depicted at FIGS. 7-9, and FIG.12. In an example where shifting to the target gear and non-target gearis not conducted, the result of the target gear and non-target gearbeing preselected, only the engine cranking via the ISG may be carriedout at 515. In other examples, only shifting to the target gear, and notto the non-target gear may be carried out at 515, in addition tocranking the engine. In still other examples, only shifting to thenon-target gear, and not to the target gear, may be carried out at 515,in addition to cranking the engine. Such examples will be furtherdiscussed below with regard to FIGS. 7-9, and FIG. 12.

Proceeding to 518, method 500 may include indicating whether crankshaftspeed is greater than the speed of the low speed input shaft. Responsiveto an indication that crankshaft speed is greater than the speed of thelow speed input shaft, method 500 may proceed to 520.

Proceeding to 520, method 500 may include applying clutch torque to thelow speed input shaft. For example, if the target gear comprises firstgear, and the non-target gear comprises sixth gear, then at 520, method500 may include applying clutch torque to the low speed input shaftcorresponding to the sixth gear. More specifically, second clutch (e.g.127) torque may be applied to the low speed input shaft (e.g. 304). Itmay be understood that the clutch torque applied to the low speed inputshaft may be controlled so that the clutch is not commanded to carrymore capacity than it is capable of achieving with reduced line pressureavailable during an engine start. Furthermore, the rate at which thetransient clutch torque is applied, as well as the peak clutch torque,may be limited to maintain enough engine torque capability to supplyboth the clutch torque and inertia torque to accelerate the crankshaftto the target gear input shaft speed in a desired amount of time.

As one example, clutch torque to the non-target, low speed input shaftmay be applied linearly up to a predetermined peak value, at a rate thatis slower than the rate at which the engine can produce increasingtorque to avoid putting more load torque on the crankshaft through theclutch than the engine is producing. In this way, sufficient crankshaftinertia torque may be preserved, to meet a desired minimum engineacceleration performance. In another example, clutch torque may beintegrated with crankshaft speed control as a secondary actuator toimprove engine and clutch torque coordination. Such an example will bediscussed in further detail with regard to FIG. 10. In still anotherexample, clutch torque may be applied in parallel with engine speedcontrol to achieve the desired behavior. Such an example will bediscussed in further detail with regard to FIG. 11.

By applying clutch torque to the low speed input shaft, the engine maytransmit positive torque through the transmission before the engine hasreached its target speed. Because the torque is going through the lowergear ratio, there may not be significant torque delivered to the wheelsto accelerate the vehicle, yet there may be enough torque to prevent theacceleration plateau and get the transmission, driveshaft, anddifferential through lash to enable faster torque application throughthe target gear ratio when the speeds are synchronized.

There may be a practical limit to how quickly torque from the engine maybe applied to the lower gear ratio (low speed) input shaft. At lowvehicle speeds, selecting the lowest gear ratio may allow the inputclutch to accept positive torque from the engine at extremely low enginespeeds. In such a case, the clutch on the low gear input shaft may neverbe fully engaged (e.g. always slipping), so torque can be transientlytransmitted through the transmission during engine starting as long asthe engine is running. However, to ensure the engine starts properly,torque capacity may in some examples not be commanded to the low speedinput shaft until stable engine combustion is confirmed. For example, aminimum engine speed may be one criteria for confirming enginecombustion (in addition to rapid engine acceleration). At very lowvehicle speeds, there may be one or more gears which may be capable ofspinning at an input speed less than the minimum engine combustionspeed. In such a situation, the method may include waiting for theengine to report that it is running normally, and then the method mayinclude selecting the highest gear ratio that puts the transmissioninput speed below crankshaft speed, giving the highest torquemultiplication through the transmission while the engine is running upto the speed of the target gear input shaft.

Proceeding to 525, method 500 may include indicating whether crankshaftspeed is synchronized with the target gear input shaft speed. As anexample, indicating whether crankshaft speed is synchronized with thetarget gear input shaft speed may comprise an indication of crankshaftspeed and target gear input shaft speed within a threshold speeddifference (e.g. a speed difference of 5% or less) of each other. Suchan indication may be provided via a Hall effect sensor (e.g. 118B)sensing crankshaft position, and target input shaft speed sensor(s)(e.g. 277). Responsive to an indication that crankshaft speed is not yetsynchronized with the target input shaft speed, method 500 may continueapplying clutch torque to the low speed (non-target) input shaft whilethe engine is running up to the speed of the target input shaft speed.

Alternatively, responsive to an indication that the crankshaft speed issynchronized with the target gear input shaft speed, method 500 mayproceed to 530, and may include applying target gear input shaft clutchtorque to the target input shaft, to connect the engine crankshaft tothe target gear input shaft. As an example, responsive to the targetgear comprising a first gear (e.g. 320), clutch torque may be applied toa first clutch (e.g. 126). In other words, at 530, method 500 mayinclude locking the target gear input clutch responsive to thecrankshaft speed being indicated to be synchronized with the target gearinput shaft speed. More specifically, at 530, locking the target gearinput clutch may comprise fully closing the target gear input clutch. Inan example where the target gear input clutch is fully closed, orlocked, it may be understood that the engine may be fully coupled, orconnected, to the driveline of the vehicle (e.g. no clutch slippage).

Proceeding to 535, method 500 may include increasing engine torque, andblending off the slipping low speed (non-target) input shaft clutchtorque capacity to transfer all of the engine torque to the target inputshaft. In other words, at 535, method 500 may include reducing the lowspeed input shaft clutch torque capacity to zero (e.g. fullydisconnecting the low speed input shaft clutch), such that all enginetorque is transferred to the transmission via the target input shaft,with no engine torque being transferred to the transmission via thenon-target input shaft. Thus, with no engine torque being transferred tothe transmission via the non-target input shaft, it may be understoodthat the engine may be fully disconnected from the non-target inputshaft of the transmission.

Accordingly, it may be understood that method 500 may include fullydisconnecting the engine crankshaft from the non-target input shaft, andconnecting the engine crankshaft to the target input shaft responsive toengine speed being synchronized with the target gear input shaft speed.It may be further understood that connecting the engine to the targetinput shaft may be accomplished via a target gear input shaft clutch,and wherein connecting and fully disconnecting the engine crankshaftfrom the non-target input shaft may be accomplished via a non-targetgear input shaft clutch.

Proceeding to 540, method 500 may include adjusting engine and electricmachine (e.g. 120), torque to achieve a requested total drivelinetorque. For example, the total driveline torque request may be afunction of driver demanded wheel torque, vehicle speed, electricmachine power limits, etc. Method 500 may then end.

Turning now to FIG. 6, an example timeline 600 is shown, illustrating anavoidance of a delay between a request for engine torque, and the enginetransmitting torque to driven wheels, according to the method of FIG. 5.Timeline 600 includes plot 605 indicating RPM of a vehicle engine (e.g.110), plot 610, indicating RPM of a dual clutch transmission odd gearinput shaft (e.g. 302), and plot 615, indicating RPM of a dual clutchtransmission even gear input shaft (e.g. 304), over time. Timeline 600further includes plot 620, indicating an engine (e.g. 110) torque, plot625, indicating ISG (e.g. 142) torque, plot 630, indicating a dualclutch transmission odd gear clutch torque, plot 635, indicating a dualclutch transmission even gear clutch torque, and plot 640, indicatingelectric machine (e.g. 120) torque, over time. Timeline 600 furtherincludes plot 645, indicating vehicle acceleration (m/s/s), over time.

At time t0, the vehicle is traveling via torque from the electricmachine only, illustrated by plot 640. The engine is off, illustrated byplots 605 and 620. The transmission input clutches (e.g. 126, 127) areopen, however the transmission has preselected a first gear (e.g. 320)on the odd shaft (e.g. 302), and a sixth gear (e.g. 330), on the evenshaft (e.g. 304). Thus, RPM of the odd shaft is greater than the RPM ofthe even shaft.

At time t1, the vehicle operator tips-in to a maximum accelerator pedal(e.g. 192) position, thus requesting maximum vehicle performance.Accordingly, between time t1 and t2, the engine is started using theISG, indicated by plot 625, and engine RPM increases, illustrated byplot 605. Furthermore, electric machine (e.g. 120) torque is increasedto a maximum limit/threshold to provide maximum electric performance,illustrated by plot 640. Accordingly, the vehicle accelerates betweentime t1 and t2, indicated by plot 645.

Between time t2 and t3, engine torque, illustrated by plot 620, iscontrolled to match engine speed, illustrated by plot 605, with thefirst gear (or target gear) input shaft speed, illustrated by plot 610.Furthermore, the clutch (e.g. second clutch 127) corresponding to thesixth gear (or non-target gear) is actuated to carry an amount ofincreasing slipping torque capacity responsive to engine speed beinghigh enough to contribute positive torque to the driveline through thetransmission. For example, engine speed being high enough to contributepositive torque to the driveline through the transmission may comprise aminimum engine speed indicating stable combustion. By actuating theclutch (e.g. closing the clutch) corresponding to the non-target inputshaft to transfer positive torque to the drive line, no plateau invehicle acceleration is indicated between time t2 and t3, illustrated byplot 645.

At time t3, engine speed, indicated by plot 605 (and thus crankshaftspeed), is indicated to be synchronized with the target (first gear)input shaft speed, illustrated by plot 610. Accordingly, the target gearinput clutch (e.g. first clutch 126) may be commanded to lock (e.g.close) responsive to the speeds being synchronized. With the target gearinput clutch locked, or commanded closed, engine torque may betransmitted to the driven wheels through the dual clutch transmission(e.g. 125). Accordingly, target gear (first gear) clutch torque isindicated to increase, indicating by plot 630. Furthermore, thenon-target (sixth gear) input clutch torque is reduced to zero torquebetween time t3 and t4, illustrated by plot 635, such that engine torqueis no longer being transmitted to the driveline via the non-target inputshaft. In other words, a capacity of the second clutch (e.g. 127)corresponding to the non-target input shaft may be blended off, oropened, thus disconnecting the engine from the driveline via thenon-target input shaft.

Thus, at time t4, with clutch capacity to the non-target input shaftreduced to zero torque, all of the engine torque is being transmitted tothe driveline via the target input shaft (e.g. 302). With engine torquebeing transmitted to the driveline via the target input shaft, thevehicle accelerates between time t4 and t5, as a function of driverdemand.

Accordingly, by using the dual clutch transmission to select twodifferent input shaft speeds during an engine start, with one shaft atthe desired target speed, and the other at a non-target speed (e.g.lower than the target speed), transient engine torque may be applied tothe driven wheels via clutch capacity through the low speed (non-target)input shaft while the engine is controlling speed to synchronize withthe target input shaft speed. Such a methodology may result in anavoidance of a vehicle acceleration plateau which may otherwise resultresponsive to a driver demanded wheel torque that exceeds a capabilityof an electric machine (e.g. 120).

Furthermore, another benefit of such a strategy is that the strategy mayutilize more of the engine's torque production capability. For example,when the engine is in speed control alone, as illustrated in thetimeline depicted at FIG. 4, it may not produce significant torque as itapproaches its target speed because it has to slow the crankshaftacceleration to synchronize with the input shaft speed. Morespecifically, at FIG. 4, engine torque, illustrated by plot 420, isreduced nearly to zero torque in order to synchronize engine speed withthe target input shaft speed at around time t3. Alternatively, reductionin engine torque may be significantly reduced to synchronize enginespeed with the target input shaft speed when method 500 is utilized, asindicated around time t3 in timeline 600 depicted at FIG. 6. Morespecifically, as illustrated at FIG. 6, the non-target input shaftclutch torque is increased as time passes, illustrated by plot 635between time t2 and t3, giving the engine most of its torque capabilityto increase crankshaft speed up to the target speed initially. As thecrankshaft speed approaches the target shaft speed, very little enginetorque may be utilized for speed regulation, and its excess torquecapability may be put into increasing the torque transmitted to thenon-target input shaft (non-target gear ratio) through the slippingclutch. Because the engine may be making significant torque at the timeof connection to the target input shaft, the engine may be able toincrease torque more quickly up to its maximum value, and more torquemay be instantly applied to the target gear input shaft as the lowerspeed (non-target) input shaft clutch torque is blended off. The resultmay be a higher peak acceleration which may be achieved quickly with noplateau in vehicle acceleration.

While the example timeline indicated at FIG. 6 illustrates an examplewhere both the target gear and the non-target gear are selected prior tothe driver demanded wheel torque exceeding the capability of theelectric machine, as discussed above at FIG. 5, there may be someexamples where shifting to either or both of the target and non-targetgear may be conducted responsive to driver demand exceeding electricmachine capability. In other examples, either or both the target gearand non-target gear may be preselected while the vehicle is operating inelectric-only mode, to prepare the transmission input shafts for theengine start procedure depicted at FIG. 5. Such examples will bediscussed below with regard to FIGS. 7-10.

Turning now to FIG. 7, a high-level example method 700 for selectinggears on both a first input shaft (e.g. 302) and second input shaft(e.g. 304) while a vehicle is operating in an electric-only mode ofoperation, is shown. Method 700 will be described with reference to thesystems described herein and shown in FIGS. 1A-3, though it should beunderstood that similar methods may be applied to other systems withoutdeparting from the scope of this disclosure. Method 700 may be carriedout by a controller, such as controller 12 in FIG. 1A, and may be storedat the controller as executable instructions in non-transitory memory.Instructions for carrying out method 700 and the rest of the methodsincluded herein may be executed by the controller based on instructionstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1A-3. The controller may employengine system actuators such as electric machine (e.g. 120), selectorforks (e.g. 372, 376, 378, 382), etc., according to the method depictedbelow.

Method 700 begins at 705 and may include indicating whether the vehicleis being operated solely in an electric mode of operation. In someexamples, a vehicle may be operating in an electric-only mode ofoperation responsive to an idle stop event, where the engine isdeactivated. Other examples may include situations where the vehicle isbeing propelled solely via the electric machine (e.g. 120). Such anindication may include an indication that the vehicle is being operatedvia an electric machine (e.g. 120), while the engine (e.g. 110) isindicated to be off, and not combusting fuel. Responsive to anindication that the vehicle is not being operated solely via theelectric-only mode of operation, method 700 may proceed to 710, and mayinclude maintaining current vehicle operating conditions. For example,if the engine is in operation, maintaining current vehicle operatingconditions may include maintaining fuel injection and maintainingproviding spark to the engine. Responsive to the electric machineadditionally being indicated to be operating, electric machine operationmay be continued. Method 700 may then end.

Returning to 705, responsive to an indication that the vehicle is beingoperated solely in an electric mode of operation, method 700 may proceedto 715. At 715, method 700 may include selecting gears with the lowestavailable speed ratios for both the first input shaft (e.g. 302) andsecond input shaft (e.g. 304). As an example, a sixth gear (e.g. 330),and a seventh gear (e.g. 332) may be selected responsive to anindication that the vehicle is operating solely in an electric mode ofoperation. More specifically, responsive to the indication that thevehicle is operating in the electric mode, one or more selector forksmay be commanded to select, or lock, the gears with the lowest availablespeed ratios, for example the sixth gear and the seventh gear. Keepingthe transmission locked in lower gear ratios may keep both input shaftsspinning while the vehicle is moving, may ensure that the system willnot overspeed transmission components, and may improve a time to shiftthe target gear shaft up to a connection speed dictated by driver demandresponsive to a driver demand exceeding the electric machine capability.Additionally, the lower gear ratios may minimize electric propulsiontorque lost to accelerating their inertia as the vehicle accelerates inelectric vehicle mode.

With the gears with the lowest available speed ratios selectedcorresponding to each input shaft, method 700 may proceed to method 500depicted at FIG. 5. In the interest of brevity, the entirety of method500 will not be reiterated here. However, it may be understood that,with the lowest available gear ratios selected while the vehicle isoperating in electric mode, responsive to drivetrain torque request at505 exceeding electric machine (e.g. 120) capability, one input shaftmay be shifted to a higher speed for a target gear at step 515, whilethe engine is accelerating and transmitting torque to the drivelinethrough the other, non-target, lower speed input shaft. In such anexample, the additional engine torque and increasing electric machinetorque at the time of increased drivetrain torque request may compensatefor the torque to increase the speed of the target shaft and prevent adecrease in vehicle acceleration resulting from the shift.

Furthermore, while the examples and description above with regard toFIG. 7 discuss shifting one input shaft to a higher speed for a targetgear, while the engine is accelerating and transmitting torque to thedriveline through the lower speed input shaft, it may be understood thatin some examples, capacity may be only applied to the clutch associatedwith the target gear, and not to the non-target gear, in response to anengine pull-up event.

While the method of FIG. 7 preselects gears with the lowest availablegear ratios while the vehicle is operating in the electric mode ofoperation, another option may be to have an algorithm that may predict atarget gear when a driver demand exceeds a capability of the electricmachine. Such an example may include keeping both input shafts locked inhigher gear ratios so that one input shaft will be at the target speedwith the engine start is demanded. Such an example may further includealways maintaining both input shafts in adjacent gear ratios, such thatalternating shafts may take turns shifting to change a target gearrange, thus minimizing a total number of gear shifts while the vehicleis being operated in electric mode. In such an example, at the time ofengine start, the non-target gear may be shifted to an appropriatenon-target, or low gear ratio, such that the clutch may be applied tothe non-target input shaft to transfer torque to the driveline while theengine is running up to the target speed. Such an example method will bediscussed below with regard to FIG. 8.

Turning now to FIG. 8, a high-level example method 800 is shown forpredicting a target gear and engaging the target gear while the vehicleis operating in an electric-only mode of operation. More specifically,method 800 may be used to predict a target gear when a driver demandexceeds a capability of an electric machine, such that the transmissiondoes not have to shift gears to the target gear subsequent to the driverdemand exceeding the capability of the electric machine. Method 800 willbe described with reference to the systems described herein and shown inFIGS. 1A-3, though it should be understood that similar methods may beapplied to other systems without departing from the scope of thisdisclosure. Method 800 may be carried out by a controller, such ascontroller 12 in FIG. 1A, and may be stored at the controller asexecutable instructions in non-transitory memory. Instructions forcarrying out method 800 and the rest of the methods included herein maybe executed by the controller based on instruction stored on a memory ofthe controller and in conjunction with signals received from sensors ofthe engine system, such as the sensors described above with reference toFIGS. 1A-3. The controller may employ engine system actuators such aselectric machine (e.g. 120), selector forks (e.g. 372, 376, 378, 382),etc., according to the method depicted below.

Method 800 begins at 805 and may include indicating whether the vehicleis being operated solely in an electric mode of operation. As discussedabove, in some examples, a vehicle may be operating in an electric-onlymode of operation responsive to an idle stop event, where the engine isdeactivated. Other examples may include situations where a vehicle isbeing propelled solely via the electric machine (e.g. 120). Such anindication may include an indication that the vehicle is being operatedvia an electric machine (e.g. 120), while the engine (e.g. 110) isindicated to be off, and not combusting fuel. Furthermore, while notexplicitly illustrated, for method 800, if the vehicle is stopped, butwhere the vehicle is being operated via electric-only operation, such asan idle-stop event, method 800 may include commanding a first gear (e.g.320) and a second gear (e.g. 322) engaged.

Responsive to an indication that the vehicle is not being operatedsolely via the electric-only mode of operation, method 800 may proceedto 810, and may include maintaining current vehicle operatingconditions. For example, if the engine is in operation, maintainingcurrent vehicle operating conditions may include maintaining fuelinjection and maintaining providing spark to the engine. Responsive tothe electric machine additionally being indicated to be operating,electric machine operation may be continued. Method 800 may then end.

Returning to 805, responsive to an indication that the vehicle is beingoperated solely in an electric mode of operation, method 800 may proceedto 815. At 815, method 800 may include determining an acceleratorposition that may result in an engine pull-up. More specifically, at815, method 800 may include determining an accelerator pedal positionthat may exceed the capacity of an electric machine (e.g. 120), suchthat in order to provide the driver demanded wheel torque, the enginemay be activated, or pulled-up.

As an example, determining accelerator pedal position which would resultin an engine pull-up at 815 may include determining or indicating acapacity of the electric machine, and determining an accelerator pedalposition for which driver demanded wheel torque may exceed the abilityof the electric machine to provide the driver demanded wheel torque. Insome examples, such an indication may be a function of a charge state ofan onboard energy storage device (e.g. 132). In some examples, such anindication may further be a function of current vehicle speed. As oneexample, the vehicle controller may include a lookup table that mayenable an accurate indication of accelerator pedal position that mayresult in driver demand exceeding the capability of the electricmachine.

With accelerator pedal position that may result in an engine pull-updetermined at 815, method 800 may proceed to 820, and may includedetermining a target gear for current vehicle speed and acceleratorpedal position that may result in an engine pull-up event. For example,as discussed above, if the vehicle is stationary, such as during an idlestop event, both the first gear and the second gear may be engaged viathe appropriate synchronizers (e.g. 370, 374, respectively).Alternatively, if the vehicle is being propelled solely via the electricmachine at non-zero speeds, then at 820, method 800 may includedetermining which target gear may be most appropriate to engage as afunction of current vehicle speed and the indicated pedal position thatmay result in an engine pull-up. As one example, the most appropriatetarget gear may be indicated or obtained via a lookup table stored atthe vehicle controller, where the lookup table may enable the mostappropriate target gear to be determined as a function of vehicle speedand accelerator pedal position that may result in an engine pull-up.

Proceeding to 825, method 800 may include indicating whether the targetgear indicated at step 820 is already engaged. For example, if thetarget gear is indicated to be second gear (e.g. 322), and second gearis already engaged by the appropriate synchronizer (e.g. 374), thenmethod 800 may proceed to 835, and may include indicating whether driverdemanded torque request exceeds the capability of the electric machine,as discussed above and which will be discussed in further detail below.

Returning to step 825, responsive to an indication that the target gearindicated at step 820 is not engaged, method 800 may proceed to 830 andmay include commanding an appropriate synchronizer to engage the targetgear. As discussed above, commanding the appropriate synchronizer toengage the target gear may comprise the controller commanding movementof the appropriate synchronizer via the appropriate selector fork, wherethe appropriate selector fork may be commanded to generate movement ofthe appropriate synchronizer via an appropriate shift fork, or selectorfork, actuator (e.g. 388). It may be understood that, the target gearmay continuously change while the vehicle is being operated with theengine off. Thus, there may be multiple shifting events to engage atarget gear while the vehicle is operating in electric mode with theengine off.

Responsive to the appropriate synchronizer engaging the target gear at830, method 800 may proceed to 835. At 835, method 800 may includeindicating whether driver demanded torque request exceeds the capabilityof the electric machine. As discussed above, such an indication mayinclude an accelerator pedal position greater than a threshold, wherethe threshold may include the pedal position determined at step 815 thatmay result in an engine pull-up. If, at 835, it is indicated that driverdemanded torque request does not exceed the capability of the electricmachine, method 800 may return to 815, and may include continuing todetermine accelerator pedal position which may result in an enginepull-up. In this way, while the vehicle is operating in electric mode,accelerator pedal position that may result in a driver demanded torquethat may exceed the capability of the electric machine may becontinually updated. Furthermore, responsive to any changes in theaccelerator pedal position which may result engine pull-up, theappropriate target gear may be continually updated and engaged, asdiscussed above.

While not explicitly illustrated, method 800 may include alwaysmaintaining both input shafts in adjacent gear ratios while the vehicleis operating in electric-only mode, regardless of the number of gearshifts that may take place prior to an engine pull-up event. As anexample, consider a vehicle that is stopped, and where electric-onlyvehicle propulsion is utilized to propel the vehicle forward uponrelease of a brake pedal (e.g. 156). In such an example, both first andsecond gears may initially be engaged while the vehicle is stopped, asdiscussed above. While the vehicle is traveling in electric-only mode,it may be determined that the target gear has become third gear, basedon accelerator pedal position that may result in an engine pull-up,vehicle speed, etc. In such an example, an appropriate synchronizer maybe commanded to engage the third gear, while the first gear may bedisengaged, thus resulting in both the second and third gear beingengaged. Subsequently, it may be determined that the fourth gear hasbecome the target gear. In such an example, an appropriate synchronizermay be commanded to engage the fourth gear, while disengaging the secondgear. In other words, both input shafts may always be maintained inadjacent gear ratios, to minimize the total number of gear shifts whilethe vehicle is being operated in electric mode. In another example, bothinput shafts may not always be maintained in adjacent gear ratios, butrather the target gear may be engaged and any most appropriate gear onthe non-target input shaft may be additionally selected, or engaged.

If, at 835, it is indicated that driver demanded torque request exceedsthe capability of the electric machine, method 800 may proceed to step515 of method 500 depicted at FIG. 5, such that the rest of method 500may be carried out. In the interest of brevity, the entirety of method500 will not be reiterated here. However, it may be understood that,with the target gear engaged according to method 800 depicted at FIG. 8,and where both the target gear and non-target gear may be maintainedengaged in adjacent gear ratios, responsive to drivetrain torque requestexceeding electric machine capability, the non-target input shaft may beshifted to an appropriate non-target low gear ratio prior to applyingclutch torque to the low speed input shaft. Thus, at step 515 of method500, the method may include cranking the engine and shifting thenon-target gear shaft to the appropriate low gear ratio. The energystored in the decelerating input shaft inertia may contribute to bothpositive torque to the transmission output to accelerate the vehicle,and may contribute additional torque to start and accelerate the engineinertia. Responsive to the engine being started and the non-target gearshaft being shifted to the appropriate low gear ratio, method 500 mayproceed as discussed above, such that an acceleration plateau, as shownin FIG. 4, may be avoided by transmitting positive torque through thenon-target input shaft clutch while the engine is running up to thetarget speed as discussed above.

While the examples of methods 700 and 800 depicted above includepreselecting gears with the lowest available speed ratios while thevehicle is operating in electric-only mode (method 700), or predicting atarget gear while maintaining both target and non-target input shafts atadjacent gear ratios (method 800), another option will be discussedbelow with regard to the method depicted at FIG. 9. Briefly, such amethod may include preselecting both the target gear and the gear forthe low speed input shaft continuously, to try and mitigate any shiftingat the time an engine start is requested.

Turning now to FIG. 9, a high-level example method 900 for predicting atarget gear and pre-engaging both the target gear and a non-target gearwhile the vehicle is operating in an electric-only mode of operation, isshown. Method 900 will be described with reference to the systemsdescribed herein and shown in FIGS. 1A-3, though it should be understoodthat similar methods may be applied to other systems without departingfrom the scope of this disclosure. Method 900 may be carried out by acontroller, such as controller 12 in FIG. 1A, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 900 and the rest of the methodsincluded herein may be executed by the controller based on instructionstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1A-3. The controller may employengine system actuators such as electric machine (e.g. 120), selectorforks (e.g. 372, 376, 378, 382), etc., according to the method depictedbelow.

Method 900 begins at 905 and may include indicating whether the vehicleis operating in an electric-only mode of operation. As discussed above,in some examples a vehicle may be operating in an electric-only mode ofoperation responsive to an idle stop event, where the engine isdeactivated. Other examples may include situations where the vehicle isbeing propelled solely via the electric machine (e.g. 120). Such anindication may include an indication that the vehicle is being operatedvia an electric machine (e.g. 120), while the engine (e.g. 110) isindicated to be off, and not combusting fuel. Other examples may includethe vehicle traveling at non-zero speed, where the vehicle is beingpropelled solely via the electric machine (e.g. 120). Responsive to anindication that the vehicle is not being operated solely via theelectric-only mode of operation, method 900 may proceed to 910, and mayinclude maintaining current vehicle operating conditions. For example,if the engine is in operation, maintaining current vehicle operatingconditions may include maintaining fuel injection and maintainingproviding spark to the engine. Responsive to the electric machineadditionally being indicated to be operating, electric machine operationmay be continued. Method 900 may then end.

Returning to 905, responsive to an indication that the vehicle is beingoperated solely in an electric mode of operation, method 900 may proceedto 915. At 915, method 900 may include determining an acceleratorposition that may result in an engine pull-up. More specifically, at915, method 900 may include determining an accelerator pedal positionthat may exceed the capacity of an electric machine (e.g. 120), suchthat in order to provide the driver demanded wheel torque, the enginemay be activated, or pulled-up.

As an example, determining accelerator pedal position which would resultin an engine pull-up at 915 may include determining or indicating acapacity of the electric machine, and determining an accelerator pedalposition for which driver demanded wheel torque may exceed the abilityof the electric machine to provide the driver demanded wheel torque. Insome examples, such an indication may be a function of a charge state ofan onboard energy storage device (e.g. 132). In some examples, such anindication may further be a function of current vehicle speed. As oneexample, the vehicle controller may include a lookup table that mayenable an accurate indication of accelerator pedal position that mayresult in driver demand exceeding the capability of the electricmachine.

With accelerator pedal position that may result in an engine pull-updetermined at 915, method 900 may proceed to 920, and may includedetermining a target gear for current vehicle speed and acceleratorpedal position that may result in an engine pull-up event. As oneexample, the most appropriate target gear may be indicated or obtainedvia a lookup table stored at the vehicle controller, where the lookuptable may enable the most appropriate target gear to be determined as afunction of vehicle speed and accelerator pedal position that may resultin an engine pull-up.

Proceeding to 925, method 900 may include indicating whether the targetgear indicated at step 920 is already engaged, and may further includeindicating whether a lowest practical gear ratio is engaged on thenon-target input shaft. For example, if the target gear is indicated tobe second gear (e.g. 322), and second gear is already engaged by theappropriate synchronizer (e.g. 374), and the lowest practical gear onthe non-target input shaft is already engaged by the appropriatesynchronizer, then method 900 may proceed to 935, and may includeindicating whether driver demanded torque request exceeds the capabilityof the electric machine, as discussed above.

Returning to step 925, responsive to an indication that the target gearindicated at step 920 is not engaged, method 900 may proceed to 930 andmay include commanding an appropriate synchronizer to engage the targetgear on one input shaft, and may further include simultaneouslycommanding an appropriate synchronizer to engage a lowest gear ratiothat enables the engine to connect to the transmission, on the othernon-target input shaft. Such a strategy may be advantageous in that itwould ideally have both the optimal target gear and the lowest practicalgear ratio on the non-target input shaft preselected before the enginestart is commanded. However, such a strategy may result in shiftinggears corresponding to both input shafts every time the current vehicleconditions indicate a change in the target gear ratio, as the currenttarget gear may thus be commanded to the lowest practical gear for thatshaft, while the other shaft may be shifted from its lowest ratio up tothe new target speed. In such a case, the inertia of the two shafts mayat least partially balance each other to reduce any torque lost from thedriveline during the shift, however in some cases any torque lost fromthe driveline during the shift may be compensated for by utilizing motortorque from the electric machine (e.g. 120), to provide a smooth shift.

Responsive to the target gear and non-target gear being indicated to beengaged via the appropriate synchronizers, which may be accomplished viathe controller commanding movement of the appropriate synchronizers viaappropriate corresponding selector forks, which may be actuated by anappropriate shift fork, or selector fork, actuator (e.g. 388), method900 may proceed to 935, and may include indicating whether driverdemanded torque request exceeds the capability of the electric machine,as discussed above.

If, at 935, it is indicated that driver demanded torque request exceedsthe capability of the electric machine, method 900 may proceed to step515 of method 500 depicted at FIG. 5, such that the rest of method 500may be carried out. In the interest of brevity, the entirety of method500 will not be reiterated here. However, it may be understood that,with both the target gear engaged on the target input shaft, and thelowest gear ratio engaged on the non-target shaft, no shifting may occurresponsive to driveline torque request exceeding electric machinecapability. Thus, at step 515 of method 500, the method may includecranking the engine and may further include maintaining the target gearengaged on the target input shaft and maintaining the non-target gearengaged on the non-target input shaft, without any shifting. Method 500may then proceed as discussed above, such that an acceleration plateau,as shown in FIG. 4, may be avoided by transmitting positive torquethrough the non-target input shaft clutch while the engine is running upto the target speed as discussed above.

As discussed above at FIG. 5 with regard to step 520 of method 500,application of clutch torque to the low speed input shaft may becontrolled so that the clutch is not commanded to carry more capacitythan it is capable of achieving with reduced line pressure availableduring an engine start. Additionally, as discussed, the rate at whichtransient clutch torque is applied, as well as the peak clutch torque,may be limited to maintain enough engine torque capability to supplyboth the clutch torque and inertia torque to accelerate the crankshaftto the target gear input shaft speed in a desired amount of time.

At step 520, one example of how clutch torque to the non-target, lowspeed input shaft may be applied included linearly applying (e.g.increasing) clutch torque to a predetermined peak value at a rate slowerthan the rate at which the engine can produce increasing torque, toavoid putting more load torque on the crankshaft through the clutch thanthe engine is producing. However, there may be additional controlmethodology to apply clutch torque to the low speed input shaft, whichwill be discussed below with regard to FIGS. 10-11. It may be understoodthat such methodology may be utilized in conjunction with method 500,and in particular with regard to step 520 of method 500, for controllingapplication of the low speed (or non-target) input shaft clutch torque.

Turning now to FIG. 10, a first block diagram 1000 for integratingclutch torque with crankshaft speed control as a secondary actuator toimprove engine and clutch torque coordination, is shown. As discussed,the method of block diagram 1000 may be used in the method of FIG. 5.Briefly, the strategy includes continuously commanding engine torque toits maximum value (e.g. threshold not to be exceeded), and the speedcontrol torque required to achieve the desired crankshaft speed may beachieved by absorbing extra torque (e.g. engine torque greater than thatused to accelerate the engine at a desired rate) directly with theappropriate low speed (non-target) dual clutch transmission input shaftclutch. In other words, the strategy may include continuously commandingengine torque to a maximum value (e.g. threshold not to be exceeded)while the engine is increasing speed to a target speed, and absorbingextra torque (e.g. engine torque greater than that used to acceleratethe engine at a desired rate) via a non-target (e.g. low speed) inputshaft clutch to transmit engine torque to the driveline and controlengine speed to the target speed. In an example where the low speed(non-target) input shaft clutch cannot absorb enough torque to get thenet torque for the crankshaft inertia to the determined value, thenengine torque may be limited for the engine speed controller.

Discussed herein, it may be understood that when operating in enginespeed control mode, engine torque may be varied to achieve a desiredengine speed. Alternatively, when operating in engine torque controlmode, engine speed may be varied to achieve a desired engine torque.

Responsive to an indication that drivetrain torque requested exceeds thecapability of the electric machine (e.g. 120), a crankshaft speed target1003 may be determined by the engine controller (e.g. 111B). Thecrankshaft speed target may be a function of an amount by which thedriver demanded torque exceeds the electric machine torque capability,for example. The crankshaft speed target may be further based on currentengine speed, accelerator pedal position, etc. A measured crankshaftspeed 1041, indicated for example via a Hall effect sensor (e.g. 118B)sensing crankshaft position, may be subtracted from crankshaft speedtarget 1003 at summing junction 1006. Output from summing junction 1006may comprise a crankshaft speed error that may be input intoproportional integral derivative (PID) engine speed controller 1007.Output from PID engine speed controller 1007 may comprise an enginespeed control torque target. The engine speed control torque target maybe subtracted from a maximum instantly available engine torque atsumming junction 1018. The output of summing junction 1018 comprising adifference between the engine speed control torque target and themaximum instantly available engine torque, may be input to junction1021. At junction 1021, a minimum (MIN) value between the output ofsumming junction 1018 and a maximum instantly available low speed(non-target) clutch torque capacity 1012, may be determined. The minimumvalue determined at junction 1021 may be input to junction 1024, where amaximum (MAX) valve between the output from junction 1021 and a zerotorque reference may be determined, such that output from junction 1024may comprise a positive torque.

Output from junction 1024 may be added to the speed control torquetarget output from summing junction 1018, at summing junction 1031.Output from summing junction 1031 may be input to an engine torquetransfer function 1034. Output from engine torque transfer function 1034may be input into an engine inertia plus dual clutch torque transferfunction 1037, along with output from junction 1024, to controlcrankshaft speed 1041. More specifically, output from junction 1024 maycomprise a value for the low speed input shaft clutch torque 1027, whichmay be included in the engine inertia plus dual clutch transmissiontorque transfer function 1037 to control crankshaft speed 1041.

In this way, the engine speed controller may continuously command enginetorque to its maximum value (e.g. threshold not to be exceeded), withextra torque going to the low speed input shaft clutch for the speedregulation.

Turning to FIG. 11, a second block diagram 1100 is shown comprising aclutch controller that works in parallel with an engine speed controllerto achieve desired behavior for providing clutch capacity to the lowspeed, non-target input shaft while the engine is running up to a targetspeed, responsive to drivetrain torque request exceeding the capabilityof the electric machine, as discussed above. The method of block diagram1100 may be used in the method of FIG. 5. Briefly, the strategy includesthe engine speed controller modulating engine torque for the crankshaftto achieve the desired speed target. In parallel, the low speedtransmission input shaft may be commanded such that excess engine torquecapability may be sent through the transmission, while preservingsufficient torque to maintain the desired acceleration responsiveness ofthe crankshaft. The net effect may be similar to the strategy depictedin FIG. 10, with the engine near its maximum torque continuously. Morespecifically, the strategy may include modulating engine torque to reacha target speed while the engine is increasing speed to a target speed,and in parallel, absorbing excess torque via a non-target clutch totransmit engine torque to the driveline and control engine speed to thetarget speed. In one example, the strategy may include modulating enginetorque to reach a target speed while the engine is increasing speed tothe target speed, and in parallel, absorbing a commanded amount ofexcess torque via a non-target clutch to transmit engine torque to thedriveline to cross lash in the system prior to connection and torquedelivery through a target clutch. In another example, the strategy mayinclude modulating engine torque to reach a target speed while theengine is increasing speed to the target speed, and in parallel,absorbing excess torque via a non-target clutch to transmit enginetorque to the driveline with the intent of preloading the engine toincrease engine response at connection and torque delivery through atarget clutch when the engine reaches the target speed.

In such examples, the non-target clutch may comprise a clutch thatcouples engine torque to a non-target (e.g. low speed) input shaft.

Responsive to an indication that drivetrain torque request exceeds thecapability of the electric machine (e.g. 120), a driver demanded wheeltorque 1103 may be subtracted from electric machine wheel torque 1106 atsumming junction 1108. Output from summing junction 1108 may comprise adriver demanded wheel torque required from the engine, while may bemultiplied at junction 1118 by 1/final drive ratio 1112 and 1/low speedtransmission gear ratio 1115, the output of which may comprise an enginetorque desired to meet the driver demanded wheel torque.

In addition, a minimum engine acceleration 1124 may be multiplied by asum of engine inertia plus flywheel inertia plus ISG inertia, atjunction 1130. It may be understood that minimum engine acceleration1124 may comprise a minimum engine/crankshaft speed acceleration desiredto maintain at a minimum. If there is any excess engine capability, itmay be sent through the transmission. The output of junction 1130 maycomprise a minimum acceleration torque, which may be subtracted from amaximum instantly available engine torque 1133, at summing junction1134. Output from summing junction 1134 may comprise a maximum excesstorque available for the dual clutch transmission low speed input shaftclutch. A minimum value between the required engine torque to meetdriver demand (outputted from junction 1118), the maximum excess torqueavailable for the dual clutch transmission, and the maximuminstantaneously available low speed clutch torque capacity 1139, may bedetermined at junction 1142. Such a minimum value obtained at junction1142 may be output to junction 1145, where a maximum value between theminimum value obtained at junction 1142 compared to a reference zerotorque may be obtained, to ensure a positive torque output from junction1145.

In addition, a difference between a crankshaft speed target 1152 and ameasured crankshaft speed 1164, may be obtained at summing junction1153. As discussed above, a crankshaft speed target 1152 may bedetermined by the engine controller (e.g. 111B). Output from summingjunction 1153 may comprise a crankshaft speed error that may be inputinto proportional integral derivative (PID) engine speed controller1007. Output from PID engine speed controller 1007 may comprise anengine speed control crankshaft torque target.

At summing junction 1159, output from the PID engine speed controller1007 comprising an engine speed control crankshaft torque target may besummed with output from an engine inertia plus dual clutch torquetransfer function 1037, where the engine inertia plus dual clutch torquetransfer function 1037 may include the output from junction 1145,comprising a low speed input shaft clutch torque. More specifically,output from junction 1145 may comprise a torque command sent to the lowspeed (non-target) dual clutch transmission input shaft clutch to absorbexcess engine torque capability to accelerate the vehicle body whilemeeting the minimum crankshaft acceleration target.

Output from summing junction 1159 may comprise a net crankshaft torquetarget, which may be input to an engine torque transfer function 1034,the output of which may feed into the engine inertia plus dual clutchtransmission torque transfer function 1037.

Accordingly, a minimum performance for the engine speed controller maybe ensured, while putting priority on sending as much torque through thetransmission as possible, and while minimizing degradation of theperformance of the engine speed controller.

Turning now to FIG. 12, another high-level example method 1200 forpredicting a target gear and in examples where a transmission of thevehicle comprises a dual clutch transmission, pre-engaging both thetarget gear and a non-target gear while the vehicle is operating in anelectric-only mode of operation, is shown. More specifically, asdiscussed above at step 515 of FIG. 5, in some examples, in response toa drivetrain torque request exceeding an electric machine capability,the target gear and the non-target gear may already be preselected.Method 700 depicted at FIG. 7 illustrates an example where the lowestavailable gear ratios are selected while the vehicle is operating inelectric mode, and in response to a drivetrain torque request exceedingelectric machine (e.g. 120) capability, one input shaft may be shiftedto a higher speed for a target gear. Method 800 depicted at FIG. 8illustrates an example where a target gear may be predicted and engagedwhile a vehicle is operating in electric mode. As discussed in relationto FIG. 8 above, method 800 may include always maintaining both inputshafts in adjacent gear ratios while the vehicle is operating inelectric-only mode, regardless of the number of gear shifts that maytake place prior to an engine pull-up event. Method 900 depicted at FIG.9 illustrates an example where a target gear may be predicted andengaged while the vehicle is operating in electric mode, and may furtherinclude engaging the lowest gear ratio on the non-target shaft.

FIG. 12 thus depicts a general method that may be used to predict andengage target gears, and in examples where the vehicle includes a dualclutch transmission, non-target gears, while a vehicle is operating inan electric mode of operation. It may be understood that, while notexplicitly illustrated, the method as depicted at FIG. 12 may be used inconjunction with the method of FIG. 5, for example, such that at step515 of method 500, a target gears, and in some examples, a non-targetgear, may be preselected while the vehicle is operating in electricmode.

Method 1200 will be described with reference to the systems describedherein and shown in FIGS. 1A-3, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 1200 may be carried out by acontroller, such as controller 12 in FIG. 1A, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 1200 and the rest of the methodsincluded herein may be executed by the controller based on instructionstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1A-3. The controller may employengine system actuators such as electric machine (e.g. 120), selectorforks (e.g. 372, 376, 378, 382), etc., according to the method depictedbelow. It may be understood that some steps of FIG. 12 are substantiallyequivalent to steps discussed above at FIG. 9, and thus, such steps willonly be briefly described in the description of method 1200.

Method 1200 begins at 1205 and includes indicating whether the vehicleis operating in an electric-only mode of operation. If, at 1205, it isindicated that the vehicle is not being operated solely via theelectric-only mode of operation, method 1200 may proceed to 1210, andmay include maintaining current vehicle operating conditions. Forexample, if the engine is in operation, engine operation may bemaintained. If the electric machine is additionally being indicated tobe operating, electric machine operation may be additionally continued.Method 1200 may then end.

Returning to 1205, in response to an indication that the vehicle isbeing operated solely in an electric mode of operation, method 1200 mayproceed to 1215. At 1215, method 1200 may include determining anaccelerator position that may result in an engine pull-up. In otherwords, an accelerator pedal position may be determined which correspondsto a circumstance where a desired wheel torque exceeds a capacity of theelectric machine (e.g. 120), thus resulting in the engine beingactivated or pulled-up, to meet the wheel torque request. In someexamples, accelerator pedal position that would result in an enginepull-up may be a function of current vehicle speed and a charge state ofan onboard energy storage device (e.g. battery). A lookup table storedat the controller may in some examples be used to indicate acceleratorpedal position that may result in driver demand exceeding the capabilityof the electric machine, as a function of vehicle speed and onboardenergy storage device charge state.

Proceeding to 1220, method 1200 may include determining a target gear(corresponding to a target gear ratio) as a function of current vehiclespeed and accelerator pedal position that may result in an enginepull-up event. Such a determination may be indicated via a lookup tablestored at the vehicle controller, for example. In other words, a shiftschedule for the transmission may be included in a lookup table storedat the vehicle controller, where such information may be retrieved inorder to indicate the target gear (corresponding to the target gearratio).

Proceeding to 1225, method 1200 may include indicating whether thetarget gear is engaged. If the target gear is not engaged, method 1200may proceed to 1230, and may include commanding the appropriatesynchronizer to engage the target gear.

Responsive to the target gear being indicated to be engaged via itsappropriate synchronizer, method 1200 may proceed to 1235, and mayinclude indicating whether the vehicle transmission is configured suchthat a secondary, or non-target gear may be selected. As an example, at1235, method 1200 may include indicating whether the vehicletransmission comprises a dual clutch transmission, such as the dualclutch transmission depicted at FIG. 3. If it is indicated that thevehicle does not include a transmission with an option to select asecondary, or non-target gear, method 1200 may end.

Alternatively, if at 1235 it is indicated that the vehicle includes atransmission with an option to select a non-target gear in addition to atarget gear, method 1200 may proceed to 1240. At 1240, method 1200 mayinclude determining the desired secondary or non-target gear.

In one example, at 1240, determining the non-target gear may includeselecting or engaging (e.g. locking) a sequentially lower gear (e.g.higher torque multiplication) than the target gear determined above at1220. In other words, if the target gear is third gear, for example,then the sequentially lower gear may comprise second gear. In such anexample, by selecting the sequentially lower gear, the transmission mayhave an appropriate gear selected (e.g. the non-target gear) in a casewhere a vehicle operator increases accelerator pedal position to aposition greater than (e.g. more pressed down) than the pedal positionthat would result in engine pull-up determined at step 1215.

In such an example, if the target gear comprises first gear, such thatthere is not an option for selecting the sequentially lower non-targetgear, then a sequentially higher gear (e.g. second gear in this case),may be selected. Such a strategy may maintain both input shafts of thetransmission locked in adjacent gear ratios, such that only one gear mayneed to be shifted at a time as vehicle inputs change enough to resultin a change in the target gear to meet driver demanded torque.

In such an example, consider a condition where the preselected gears(corresponding to preselected gear ratios) for both input shafts are notcorrect to meet driver demanded torque at a time where an engine starthas been commanded. The strategy outlined above provides that areasonable gear ratio is selected, thus enabling the engine to quicklystart and connect to one of the preselected gears, and then to downshiftto the final correct, or optimal, gear ratio. In this example, becausethe target gear is selected based on the minimum pedal position thatwould result in an engine start event, in the case where pedal positionsare significantly more pressed down than the pedal position which wouldresult in an engine start event, a downshift from the target gear maymeet the driver demand.

In another example, at 1240, determining the non-target gear may includeselecting or engaging (e.g. locking) a sequentially higher gear (e.g.lower torque multiplication) than the target gear determined above at1220. In other words, if the target gear is third gear, for example,then the sequentially higher gear may comprise fourth gear. In such anexample, the non-target gear may be more appropriate than the targetgear, in situations where the engine is started in order to maintainbattery charge, provide cabin heating, or meet some other requirementother than meeting total vehicle operator torque request.

In such an example, if the target gear determined at 1220 comprises thehighest gear (e.g. lowest torque multiplication) of the transmission, orin a case where the transmission input shaft speed corresponding to thenext highest gear is below an engine idle speed, then the method mayinclude selecting a sequentially next lower gear (e.g. higher torquemultiplication) with respect to the target gear. Such a strategy maymaintain both input shafts of the transmission locked in adjacent gearratios, such that only one gear may be shifted at a time as vehicleinputs change enough to result in a change in the target gear to meetdriver demanded torque.

In this example where a sequentially higher gear than the target gear isselected, consider a condition where the preselected gears(corresponding to gear ratios) are not correct to meet driver demandedtorque at a time an engine start has been commanded, the strategyoutlined provides that a reasonable gear ratio is selected, thusenabling the engine to quickly start and connect to one of thepreselected gears, and then to shift into the final correct, or optimal,gear ratio. In this example, because the target gear is selected basedon the minimum pedal position that would result in and engine start, adownshift may meet driver demand from pedal positions significantly morepressed down than the minimum pedal position that would result in anengine start. Alternatively, if the engine is being started to meet avehicle condition other than driveline torque, such a strategy mayinclude connecting to the lowest gear ratio currently selected, orlocked, and may then include upshifting to a more appropriate gear ratioif the preselected gear ratio is low enough.

In still another example, at 1240, determining the non-target gear mayinclude selecting a gear (corresponding to a gear ratio) on thenon-target input shaft that is appropriate for a current vehicle state,for example appropriate for current accelerator pedal position andvehicle speed. Because only the non-target shaft may be utilized toselect such a gear ratio, and because not all gears are represented onthe non-target shaft due to the configuration of a dual clutchtransmission (see FIG. 3), such a selection may comprise a gear higheror lower than an optimal gear. Such a selection may provide that if theengine were to be started to meet some vehicle requirement other thanmeeting drivetrain torque (e.g. cabin heating, battery charging), anappropriate gear would already be selected. In such a case, consider acondition where the driver increases pedal position to the minimum pedalposition that would result in an engine start. In this example, anappropriate gear would also already be preselected (e.g. the targetgear). In either case discussed, the vehicle controller may shift afterthe engine connects, for example if the accelerator pedal is morepressed down than the minimum pedal position which would result in anengine start, or if the target and non-target gears (corresponding togear ratios) are not optimal at the time of engine start. Thus, such astrategy ensures that reasonable gears for connection are preselectedfor engine start commands based on accelerator pedal position and/orengine demand resulting from vehicle requirements other than meetingdrivetrain torque requests.

In response to the secondary, or non-target gear being determined at1240, method 1200 may proceed to 1245. At 1245, method 1200 may includeindicating whether the non-target gear is engaged. If the non-targetgear is engaged, the method may end. Alternatively, if it is indicatedat 1245 that the non-target gear is not engaged, method 1200 may proceedto 1250. At 1250, method 1200 may include commanding an appropriatesynchronizer to engage the non-target gear. Similar to that discussedabove, commanding the appropriate synchronizer to engage the non-targetgear may comprise the controller commanding movement of the appropriatesynchronizer via the appropriate selector fork, where the appropriateselector fork may be commanded to generate movement of the appropriatesynchronizer via an appropriate shift fork, or selector fork, actuator.

While not explicitly shown, it may be understood that, the target gearand non-target gear may in some examples continuously change while thevehicle is being operated with the engine off as a function of driverdemand. Thus, there may be multiple shifting events to engage a targetgear/non-target gear while the vehicle is operating in electric modewith the engine off.

In a variation of method 1200, at step 1215, rather than determining aminimum accelerator pedal position that may result in an engine pullupevent, the method may include predicting an optimal transmission gearratio provided that the accelerator pedal position is pushed down 100%,or fully pressed down, and further based on vehicle inputs such asvehicle speed, for example. In such an example, the transmission maypredictively shift and lock the transmission in this gear ratio,allowing the vehicle to quickly respond to extreme driver demand toachieve the best vehicle acceleration response. If the vehicle is a dualclutch transmission (see step 1235), then an additional gear ratio(non-target gear) may be locked to provide an alternate gear ratio, asdiscussed above. One example may include selecting or engaging asequentially higher gear than the target gear, so that the transmissionwill have the next gear selected to prepare for an upshift if thevehicle operator were to continue to accelerate after the engine hasbeen connected to the transmission via the target gear. Also, in a casewhere the vehicle operator depressed the accelerator pedalsignificantly, but not all the way to fully pressed down (100% presseddown), then the non-target gear (sequentially higher than the targetgear) may not provide as much torque multiplication, and thus may enablethe engine to directly connect at an optimal gear ratio for that driverdemand.

In such an example, if the first or target gear is already the highestgear (lowest torque multiplication), or if the transmission input shaftspeed at the next highest gear is below an engine idle speed, thevehicle controller may instead command the sequentially lower gear (thanthe target gear). Such a strategy may position transmission gear ratiosto quickly respond to high drivetrain torque requests.

In this example, consider a condition where the engine is requested tobe started to meet a lower torque request, or to maintain batterycharge, cabin heating, etc. In such an case, a shift to a moreappropriate gear ratio (lower torque multiplication) prior to connectingthe engine to reduce engine speed and sound volume at connection, and toreduce potential driveline disturbance. Because such engine startcommands to meet a lower torque request or to maintain battery charge,initiate/maintain cabin heating, etc., may occur without a quick,dynamic response, such requests may not result in a significantdrivetrain torque request change. Thus, a transmission shift event maybe commanded under such conditions just prior to engine start, where theshift event may not adversely affect the driveline. Also, in the casewhere the transmission is shifted to a gear resulting in a lowertransmission input speed and torque multiplication, such a shift may notrely on torque from the driveline to be completed, as positive torquemay flow from decelerating transmission components out to the wheels, orpotentially out to the engine in response to engaging or partiallyengaging one of the transmission input clutches. Using the inputclutches to dissipate the positive inertia torque may potentially leadto smoother vehicle dynamics during such a shift to a lower torquemultiplication gear.

Thus, a system for a vehicle may comprise an engine, a transmissionselectively coupled to the engine via one or more clutches, thetransmission including one or more shifting elements, an electricmachine positioned downstream of the transmission, an electrictransmission oil pump, and a controller. The controller may storeinstructions in non-transitory memory that, when executed, cause thecontroller to propel the vehicle via the electric machine while theengine is disconnected from the transmission via the one or moreclutches being fully open, pre-engage one or more gears of thetransmission to prepare for an engine start event, the engine startevent in response to a driveline torque request that exceeds acapability of the electric machine. In such an example, pre-engaging theone or more gears may include operating the electric transmission oilpump to provide hydraulic pressure to control the one or more shiftingelements to pre-engage the one or more gears.

In one example of the system, the shifting elements includes one or moreselector forks and one or more synchronizers.

In one example of the system, the controller may store additionalinstructions to at least partially connect the engine to thetransmission in response to the engine start event, in order to transferengine torque to the transmission, where the transmission includes theone or more pre-engaged gears and to meet the driveline torque request.In such an example, pre-engaging one or more gears may be based on atleast a position of an accelerator pedal and a current vehicle speed,and wherein pre-engaging the one or more gears includes one or more gearshift events while the vehicle is being propelled via the electricmachine.

Turning now to FIG. 13, an example method for an engine start whenselected gears correspond to gears desired in the event that a vehicleoperator steps down on an accelerator pedal 100%, or substantiallyequivalent to 100%, but where the engine start is commanded based on alower torque request, such as to charge a battery, initiate/maintaincabin heating, etc., is shown.

Method 1300 will be described with reference to the systems describedherein and shown in FIGS. 1A-3 though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 1300 may be carried out by acontroller, such as controller 12 in FIG. 1A, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 1300 and the rest of the methodsincluded herein may be executed by the controller based on instructionstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1A-3. The controller may employengine system actuators such as electric machine (e.g. 120), selectorforks (e.g. 372, 376, 378, 382), etc., according to the method depictedbelow.

Method 1300 begins at 1305, and may include indicating whethertarget/non-target gears in a dual clutch transmission areselected/engaged such that said target/non-target gears are gears chosento meet driver demand in response to a vehicle operator stepping into anaccelerator pedal 100%, or substantially equivalent to 100%.Furthermore, at 1305, it may be indicated whether the engine is off. If,at 1305, it is indicated that the target/non-target gears are notselected as a function of 100% accelerator pedal position, or if theengine is in operation, method 1300 may proceed to 1308, and may includemaintaining current vehicle operating parameters. Maintaining currentvehicle operating parameters may include maintaining the transmission inits current operational state, maintaining the engine and electricmachine in their current operational state, etc. Method 1300 may thenend.

Returning to 1305, if it is indicated that the target/non-target gearsselected are based on meeting 100% accelerator pedal demand, method 1300may proceed to 1310. At 1310, method 1300 may include indicating whetherand engine start is requested to maintain or charge a high voltagebattery, heat the vehicle cabin, etc. If an engine start request is notindicated to be requested, method 1300 may proceed to 1308 and mayinclude maintaining current vehicle operating conditions, as discussedabove.

Alternatively, if at 1310 it is indicated that the engine is requestedto start to maintain or charge a high voltage battery, heat the vehiclecabin, etc., then method 1300 may proceed to 1315. At 1315, method 1300may include determining an optimal gear for the engine start request.Such an optimal gear may comprise a gear with lower torquemultiplication than the gears selected to meet 100% pedal demand, forexample.

Subsequent to determining the optimal gear for the engine start request,method 1300 may proceed to 1320. At 1320, method 1300 may includecommanding the lowest selected gear to a neutral position. Morespecifically, the appropriate synchronizer for the lowest selected gearmay be commanded via the vehicle controller to disengage the lowestselected gear to a neutral position, via an appropriate selector fork,where the selector fork may be commanded to generate movement of theappropriate synchronizer via an appropriate selector fork actuator.

Subsequent to commanding the lowest selected gear to a neutral position,method 1300 may proceed to 1325. At 1325, method 1300 may includecommanding engine speed to a desired optimal gear input shaftsynchronous speed. Engine speed may be controlled via torque actuators,such as fuel injectors, throttle, etc. The optimal gear input shaftspeed may be indicated as a function of current vehicle speed, and agear ratio corresponding to the optimal gear for the engine startrequest.

Proceeding to 1330, method 1300 may include commanding closed the clutchcorresponding to the input shaft with the gear in neutral, to reduceinput shaft speed to the optimal gear input shaft synchronous speed.With the input shaft in neutral, clutch torque transfer between theengine and decelerating transmission components may be isolated from thedriveline and vehicle dynamics, which may reduce or eliminate anypotential drivetrain disturbance.

Continuing to 1335, method 1300 may include indicating whether enginespeed is substantially equivalent to the speed of the input shaftcorresponding to the optimal gear, where both the engine speed and theinput shaft speed corresponding to the optimal gear are substantiallyequivalent to the input shaft synchronous speed for the optimal gear.Responsive to an indication that the engine speed and input shaft speedcorresponding to the optimal gear are substantially equivalent, method1300 may proceed to 1340. At 1340, method 1300 may include commandingopen the clutch corresponding to the input shaft with the gear inneutral, and may further include the vehicle controller commanding theappropriate synchronizer to engage the optimal gear for the engine startrequest. Because the components of the transmission are at the correctrelative speeds for the optimal gear for the engine start request, sucha shift may be smooth with an added benefit of reduced wear on thesynchronizer and with reduced engagement noise.

Proceeding to 1345, responsive to engaging the optimal gear, method 1300may include applying capacity to the clutch corresponding to the inputshaft of the optimal gear, to connect and lock the engine to thetransmission and driveline in the optimal gear for the engine startrequest. Throughout the entirety of method 1300, the other input shaftmay remain with the gear engaged corresponding to a gear that may meet100% pedal demand, as discussed above, such that the gear iscontinuously available for the engine to connect to if driver demandchanges significantly to request a significant increase in drivetrainoutput torque.

Turning now to FIG. 14, an example timeline 1400 for pre-selecting oneor more gears (corresponding to gear ratios) in a transmission while thevehicle is operating in an electric mode of operation, is shown. Morespecifically, the pre-selected gears include gears pre-selected in theevent that the vehicle operator fully steps down on the acceleratorpedal, thus requesting a significant amount of increased drivelinetorque. Timeline 1400 illustrates a gear shift responsive to anindication of an engine start request, under conditions where theaccelerator pedal remains less than fully pressed down, and where theengine is requested to maintain battery charge, heat the vehicle cabin,etc.

Timeline 1400 includes plot 1405, indicating an accelerator pedalposition, over time. The accelerator pedal may be released (0), or maybe pressed further down (+), where pressing down on the acceleratorpedal indicates a request for greater acceleration. Line 1406 representsa threshold amount where, if reached, indicates that the acceleratorpedal is fully pressed down (e.g. 100% pressed down). Timeline 1400further includes plot 1410, indicating a speed (RPM) of an engine, plot1415, indicating RPM of a dual clutch transmission odd gear input shaft(e.g. 302), and plot 1420, indicating RPM of a dual clutch transmissioneven gear input shaft (e.g. 304), over time. Timeline 1400 furtherincludes plot 1425, indicating a gear selection corresponding to the oddgear input shaft, and plot 1430, indicating a gear selectioncorresponding to the even gear input shaft, over time. In this exampletimeline 1400, it may be understood that gears selected may includegears 1-6, and under conditions where the gear is not selected orengaged, the gear may be in a neutral (N) configuration. Timeline 1400further includes plot 1435, indicating whether an engine start event isrequested (yes), or not (no), over time. Timeline 1400 further includesplot 1440, indicating odd input shaft clutch torque, and plot 1445,indicating even input shaft clutch torque, over time. It may beunderstood that when clutch torque is 0, the clutch if fully open, andincreases in clutch torque are indicated via a (+).

At time t0, while not explicitly shown, it may be understood the vehicleis being propelled solely in an electric mode of operation. However, toprepare for an increase in driveline torque request, a gear ispreselected on the odd input shaft, and a gear is preselected on theeven input shaft. More specifically, third gear is preselected on theodd input shaft, while second gear is preselected on the even inputshaft. Accordingly, it may be understood that, in this example, gearpreselection is conducted according to method 1300, depicted above atFIG. 13. As such, the preselected gears represent desired or optimalgears under conditions where the vehicle operator requests a significantamount of increased wheel torque, for example under conditions where thevehicle operator steps down on the accelerator pedal 100%, orsubstantially equivalent to 100%.

Between time t0 and t1, the engine is off, indicated by plot 1410, andbecause the second and third gears are engaged, their respective eveninput shaft RPM (e.g. 1420, 1415 respectively) is a function of theengaged gears. More specifically, because second gear comprises a highertorque multiplication than third gear, the even input shaft RPM ishigher than the odd input shaft RPM. Furthermore, both input clutchescorresponding to the input shafts are fully open, indicated by plots1440 and 1445. Thus, even though the input shafts are spinning, notorque is transferred to the engine. Still further, accelerator pedalposition is less than fully pressed down, thus an engine start event isnot requested.

At time t1, an engine start event is indicated to be requested, howeverthe engine start request is not due to the accelerator pedal beingpressed down 100%. Instead, it may be understood that the engine startrequest relates to one or more of a request for battery charging, cabinheating/cooling, etc. In such an example, the vehicle controller maydetermine that a most appropriate gear to be engaged for engine startingis a higher gear than those preselected. In this example timeline 1400,it may be understood that the vehicle controller indicates that theideal or most appropriate/optimal gear is sixth gear. Accordingly, thelowest preselected gear (second gear in this example) is disengaged viaits appropriate synchronizer, to a neutral state.

With the lowest preselected gear in neutral, between time t1 and t2,capacity is applied to the even input shaft clutch, such that even inputshaft clutch torque increases. Engine speed is controlled to a sixthgear input shaft synchronous speed, calculated from current vehiclespeed and sixth gear ratio. Accordingly, even input shaft RPMs decrease,and clutch torque is controlled to control even input shaft RPM to match(e.g. within 5% or less) of the engine speed, which is being controlledto maintain the sixth gear input shaft synchronous speed.

At time t2, engine speed and even input shaft speed are substantiallyequivalent. Thus, the even input shaft clutch is commanded open,resulting in a decrease in clutch torque between time t2 and t3. At timet3, an appropriate synchronizer is controlled via the vehicle controllerto engage, or lock, the sixth gear. With the sixth gear locked, capacityto the even input shaft clutch is again applied, to connect the engineto the transmission and driveline in sixth gear. By connecting theengine in sixth gear, the increased driveline torque request may be metbetween time t3 and t4, without significant driveline torquedisturbance, noise, wear and tear on synchronizers, etc. Furthermore,throughout the example timeline 1400, third gear is maintained engaged,and it may thus be understood that third gear is continuously availablefor the engine to connect to under conditions where the driver changedaccelerator pedal position suddenly to request a significant increase indrivetrain output torque.

In this way, while a vehicle is being propelled via power from anelectric machine, where an engine is disconnected from the transmission,the transmission may be configured in optimal gear(s) prior to theengine being commanded to start and connect to the driveline.Pre-selecting the gears may be conducted via hydraulic pressure providedvia an auxiliary electric transmission oil pump, to actuate shiftelements inside the transmission while the engine is stopped and thevehicle is being driven only by electric propulsion. In a case where thevehicle transmission comprises a dual clutch transmission, two gearratios may be preselected or locked prior to an engine start, which mayincrease a likelihood that an optimal gear is pre-selected.

The technical effect is to recognize that there may be different optionsfor engaging gears in the transmission while the vehicle is operating inelectric only drive mode, to prepare the transmission input shafts foran engine start procedure. Examples may include 1) always havingavailable gears with the lowest available speed ratios selected inelectric-only propulsion mode, and then shifting the desired input shaftup to the higher speed required for the target gear while the engine isaccelerating and transmitting torque through the other shaft, 2) havingan algorithm predict the target gear when a driver demand exceeds thecapability of the electric machine, or 3) having an algorithm preselectboth the target gear and the non-target gear to mitigate any shifting atthe time an engine start is requested, etc. Such algorithms have beendiscussed in detail above in the detailed description.

The systems described herein, and with reference to FIGS. 1A-3, alongwith the methods described herein, and with reference to FIG. 5 andFIGS. 7-13, may enable one or more systems and one or more methods. Inone example, a driveline operating method comprises propelling a vehiclesolely via an electric machine while an engine of the vehicle is off andnot connected to a transmission, the electric machine positioned in thedriveline downstream of the transmission; and engaging one or more gearsof the transmission with the engine off, to prepare the driveline for anengine start event to meet a vehicle operator torque request. In a firstexample of the method, the method further includes wherein engaging oneor more gears further comprises engaging one or more gears with a lowesttorque multiplication available that allows an input shaft to thetransmission to remain above an engine idle speed while the vehicle ispropelled solely via the electric machine. A second example of themethod optionally includes the first example, and further comprisesshifting the one or more gears to another gear to meet the vehicleoperator torque request prior to connecting the engine to thetransmission. A third example of the method optionally includes any oneor more or each of the first and second examples, and further comprisespredicting vehicle operating conditions that will result in the enginestart event. A fourth example of the method optionally includes any oneor more or each of the first through third examples, and furtherincludes wherein the vehicle operating conditions that result in theengine start event include a minimum accelerator pedal position and acurrent vehicle speed. A fifth example of the method optionally includesany one or more or each of the first through fourth examples, andfurther includes wherein engaging the one or more gears of thetransmission further comprises engaging a target gear comprising anoptimal gear for connecting the engine to the transmission at the timeof the engine start event. A sixth example of the method optionallyincludes any one or more or each of the first through fifth examples,and further includes wherein engaging the one or more gears of thetransmission further comprises additionally engaging a non-target gear,where the transmission comprises a dual clutch transmission. A seventhexample of the method optionally includes any one or more or each of thefirst through sixth examples, and further includes wherein thenon-target gear comprises a sequentially lower gear than the targetgear, provided that the target gear is not the lowest available gear. Aneighth example of the method optionally includes any one or more or eachof the first through seventh examples, and further includes wherein thenon-target gear comprises a sequentially higher gear than the targetgear, provided that the target gear is not the highest available gear. Aninth example of the method optionally includes any one or more or eachof the first through eighth examples, and further includes wherein thetarget gear comprises the optimal gear for connecting the engine to thetransmission at the time of the engine start event, and where thenon-target gear corresponds to an appropriate gear ratio for a currentaccelerator pedal position and vehicle speed. A tenth example of themethod optionally includes any one or more or each of the first throughninth examples, and further includes wherein engaging the one or moregears further comprises operating an electric transmission pump toprovide hydraulic fluid to actuate one or more shift elements of thetransmission.

Another example of a driveline operating method comprises propelling avehicle solely via an electric machine while an engine of the vehicle isoff and not connected to a transmission, the electric machine positionedin the driveline downstream of the transmission; predicting and engaginga target transmission gear while the engine is off to prepare thedriveline for an engine start event responsive to an operator of thevehicle pressing down on an accelerator pedal greater than a thresholdaccelerator pedal position. In a first example of the method, the methodfurther includes wherein the threshold accelerator pedal positioncomprises an accelerator pedal position substantially equivalent to 100%pressed down, or fully pressed down. A second example of the methodoptionally includes the first example, and further comprisesadditionally engaging a non-target gear, the non-target gear comprisinga sequentially higher or sequentially lower gear than the target gear. Athird example of the method optionally includes any one or more or eachof the first and second examples, and further includes wherein theengine start event is not a result of the accelerator pedal positiongreater than the threshold accelerator pedal position, but the result ofa lower torque request, the lower torque request including a request forheating/cooling of a cabin of the vehicle and/or a request to charge abattery of the vehicle. A fourth example of the method optionallyincludes any one or more or each of the first through third examples,and further comprises in response to the lower torque request,indicating a desired gear higher than the target gear and non-targetgear to engage to meet the lower torque request; disengaging thenon-target gear or the target gear to a neutral configuration;controlling an engine speed to a transmission input shaft synchronousspeed corresponding to the desired gear, the transmission input shaftsynchronous speed corresponding to a speed of a transmission input shaftwhen the desired gear is engaged at a current vehicle speed; commandingcapacity to a clutch corresponding to the transmission input shaft toreduce the speed of the transmission input shaft to the engine speedcontrolled to the transmission input shaft synchronous speed; fullyopening the clutch corresponding to the transmission input shaftresponsive to the speed of the transmission speed being substantiallyequivalent to the engine speed; engaging the desired gear subsequent tofully opening the clutch; and commanding capacity to the clutchsubsequent to the engaging of the desired gear to connect the engine tothe transmission to meet the lower torque request. A fifth example ofthe method optionally includes any one or more or each of the firstthrough fourth examples, and further comprises connecting the engine tothe transmission at the target gear in response to the vehicle operatorpressing down on the accelerator pedal greater than the thresholdaccelerator pedal position.

An example of a system for a vehicle comprises an engine; a transmissionselectively coupled to the engine via one or more clutches, thetransmission including one or more shifting elements; an electricmachine positioned downstream of the transmission; an electrictransmission oil pump; and a controller storing instructions innon-transitory memory that, when executed, cause the controller to:propel the vehicle via the electric machine while the engine isdisconnected from the transmission via the one or more clutches beingfully open; pre-engage one or more gears of the transmission to preparefor an engine start event, the engine start event in response to adriveline torque request that exceeds a capability of the electricmachine, where pre-engaging the one or more gears includes operating theelectric transmission oil pump to provide hydraulic pressure to controlthe one or more shifting elements to pre-engage the one or more gears.In a first example of the system, the system further includes whereinthe one or more shifting elements includes one or more selector forksactuators and one or more synchronizers. A second example of the systemoptionally includes the first example, and further comprises additionalinstructions to at least partially connect the engine to thetransmission in response to the engine start event, in order to transferengine torque to the transmission where the transmission includes one ormore pre-engaged gears and to meet the driveline torque request; andwherein pre-engaging one or more gears is based on at least a positionof an accelerator pedal and a current vehicle speed, and whereinpre-engaging the one or more gears includes one or more gear shiftevents while the vehicle is being propelled via the electric machine.Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A driveline operating method, comprising:propelling a vehicle solely via an electric machine while an engine ofthe vehicle is off and not connected to a dual clutch transmission, theelectric machine positioned in a driveline downstream of thetransmission; and engaging a first target gear with a first target inputshaft to the transmission and engaging a first non-target gear with afirst non-target input shaft to the transmission with the engine off andwhile first and second clutches of the dual clutch transmission are openin response to entering a driveline mode where the vehicle is propelledsolely via the electric machine.
 2. The method of claim 1, furthercomprising engaging the first target gear with a lowest torquemultiplication available that allows the first target input shaft to thetransmission to remain above an engine idle speed while the vehicle ispropelled solely via the electric machine.
 3. The method of claim 1,further comprising shifting to a second target gear in response to arequest to start the engine, the second target gear determined as afunction of an amount a requested driveline torque exceeds a torquecapability of the electric machine.
 4. The method of claim 1, whereinthe dual clutch transmission includes a total of two clutches.
 5. Themethod of claim 1, wherein the first non-target gear comprises asequentially lower gear than the first target gear.
 6. The method ofclaim 1, wherein the first non-target gear comprises a sequentiallyhigher gear than the first target gear.
 7. The method of claim 1,wherein the first target gear comprises an optimal gear for connectingthe engine to the transmission at a time of an engine start event, andwhere the first non-target gear corresponds to an appropriate gear ratiofor a current accelerator pedal position and vehicle speed.
 8. Themethod of claim 1, further comprising operating an electric transmissionpump to provide hydraulic fluid to actuate one or more shift elements ofthe transmission in order to engage the first target gear and the firstnon-target gear, the one or more shift elements comprising one or moreselector fork actuators and one or more synchronizers.
 9. The method ofclaim 1, further comprising predicting vehicle operating conditions thatwill result in an engine start event.
 10. The method of claim 9, whereinthe predicting includes a threshold accelerator pedal position and/or acurrent vehicle speed.
 11. A driveline operating method, comprising:propelling a vehicle solely via an electric machine while an engine ofthe vehicle is off and not connected to a dual clutch transmission, theelectric machine positioned in a driveline downstream of thetransmission; predicting and engaging a first target transmission gearand a first non-target transmission gear while the engine is off inresponse to entering a driveline mode where the vehicle is propelledsolely via the electric machine, and where first and second clutches ofthe dual clutch transmission are open while the engine is off and thefirst target transmission gear and the first non-target transmissiongear are engaged.
 12. The method of claim 11, further comprisingstarting the engine in response to an accelerator pedal position beingsubstantially equivalent to 100% pressed down, or fully pressed down.13. The method of claim 11, wherein engaging the first non-targettransmission gear comprises engaging a sequentially higher or asequentially lower gear than the first target transmission gear.
 14. Themethod of claim 11, further comprising connecting the engine to the dualclutch transmission via the second clutch in response to an engine startrequest.
 15. The method of claim 11, further comprising starting theengine in response to a request for heating/cooling of a cabin of thevehicle and/or a request to charge a battery of the vehicle.
 16. Themethod of claim 15, further comprising, in response to the request forheating/cooling of the cabin and/or the request to charge the battery:disengaging either the first non-target transmission gear or the firsttarget transmission gear to a neutral configuration; and engaging adesired gear that is higher than the first target transmission gear andthe first non-target transmission gear in response to the request.
 17. Asystem for a vehicle, comprising: an engine; a transmission selectivelycoupled to the engine via two clutches, the transmission including oneor more shifting elements; an electric machine positioned downstream ofthe transmission; an electric transmission oil pump; and a controllerstoring instructions in non-transitory memory that, when executed, causethe controller to: propel the vehicle via the electric machine while theengine is disconnected from the transmission via the two clutches beingfully open; pre-engage a first target gear of the transmission and afirst non-target gear of the transmission while propelling the vehiclesolely via the electric machine, selecting the first non-target gear inresponse to accelerator pedal position and vehicle speed, and startingthe engine in response to a driveline torque request that exceeds acapability of the electric machine, and where pre-engaging the firsttarget gear and the first non-target gear includes operating theelectric transmission oil pump to provide hydraulic pressure to controlthe one or more shifting elements to pre-engage the first target gearand the first non-target gear.
 18. The system of claim 17, wherein theone or more shifting elements include one or more selector forkactuators and one or more synchronizers, and where the transmissionincludes a total of two clutches.
 19. The system of claim 17, furthercomprising additional instructions to at least partially connect theengine to the transmission in response to the engine being started inorder to transfer engine torque to the transmission to meet thedriveline torque request; and wherein pre-engaging the first target gearand the second non-target gear is based on at least a position of anaccelerator pedal and a current vehicle speed, and wherein pre-engagingthe first target gear and the first non-target gear includes one or moregear shift events while the vehicle is being propelled via the electricmachine.